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Cisco's implementation of the Internet Protocol (IP) suite provides all major services contained in the TCP/IP specifications.
Use the commands in this chapter to configure and monitor the IP routing protocols. For IP routing protocol configuration information and examples, refer to the "Configuring IP Routing Protocols" chapter of the Router Products Configuration Guide.
Use the aggregate-address router configuration command to create an aggregate entry in a BGP routing table. Use the no form of this command to disable this feature.
aggregate-address address mask [as-set] [summary-only] [suppress-map map-name]
address | Aggregate address. |
mask | Aggregate mask. |
as-set | (Optional) Generates autonomous system set path information. |
summary-only | (Optional) Filters more specific routes from updates. |
suppress-map map-name | (Optional) Name of route-map to suppress. |
Disabled
Router configuration
You can implement aggregate routing in BGP either by redistributing an aggregate route into BGP or by using this conditional aggregate routing feature.
Using the aggregate-address command with no arguments will create an aggregate entry in the BGP routing table if there are any more-specific routes available that fall in the specified range. The aggregate route will be advertised as coming from your autonomous system and has the atomic aggregate attribute set to show that information might be missing. (By default, the atomic aggregate attribute is set unless you specify the as-set keyword in the aggregate-address command.)
Using the as-set keyword creates an aggregate entry using the same rules that the command follows without this keyword, but the path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized. Do not use this form of aggregate-address when aggregating many paths, because this route must be continually withdrawn and re-updated as autonomous system path reachability information for the summarized routes changes.
Using the summary-only keyword not only creates the aggregate route (for example, 193.*.*.*) but will also suppress advertisements of more specific routes to all neighbors. If you only want to suppress advertisements to certain neighbors, you may use the neighbor distribute-list command, with caution. If a more-specific route leaks out, all BGP speakers will prefer that route over the less- specific aggregate you are generating (using longest-match routing).
Using the suppress-map keyword creates the aggregate route but suppresses advertisement of specified route maps. You can use the match clauses of route maps to selectively suppress some more specific routes of the aggregate and leave others unsuppressed. IP access lists and AS path access lists match clauses are supported.
In the following example, an aggregate address is created. The path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized.
router bgp 5
aggregate-address 193.0.0.0 255.0.0.0 as-set
match ip address
match as-path
route-map
area-id | Identifier of the area for which authentication is to be enabled. The identifier can be specified as either a decimal value or an IP address. |
Type 0 authentication (no authentication)
Router configuration
Specifying authentication for an area sets the authentication to Type 1 (simple password) as specified in RFC 1247. If this command is not included in the configuration file, authentication of Type 0 (no authentication) is assumed.
The authentication type must be the same for all routers in an area. The authentication password for all OSPF routers on a network must be the same if they are to communicate with each other via OSPF. Use the ip ospf authentication-key interface configuration command to specify this password.
The following example mandates authentication for areas 0 and 36.0.0.0 of OSPF routing process 201. Authentication keys are also provided.
interface ethernet 0
ip address 131.119.251.201 255.255.255.0
ip ospf authentication-key adcdefgh
!
interface ethernet 1
ip address 36.56.0.201 255.255.0.0
ip ospf authentication-key ijklmnop
!
router ospf 201
network 36.0.0.0 0.255.255.255 area 36.0.0.0
network 131.119.0.0 0.0.255.255 area 0
area 36.0.0.0 authentication
area 0 authentication
area default-cost
area stub
ip ospf authentication-key
area-id | Identifier for the stub area. The identifier can be specified as either a decimal value or as an IP address. |
cost | Cost for the default summary route used for a stub area. The acceptable value is a 24-bit number. |
Cost of 1
Router configuration
This command is used only on an area border router attached to a stub area.
There are two stub area router configuration commands: the stub and default-cost options of the area command. In all routers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an area border router attached to the stub area. The default-cost option provides the metric for the summary default route generated by the area border router into the stub area.
The following example assigns a default-cost of 20 to stub network 36.0.0.0:
interface ethernet 0
ip address 36.56.0.201 255.255.0.0
!
router ospf 201
network 36.0.0.0 0.255.255.255 area 36.0.0.0
area 36.0.0.0 stub
area 36.0.0.0 default-cost 20
area authentication
area stub
area-id | Identifier of the area about which routes are to be summarized. It can be specified as either a decimal value or as an IP address. |
address | IP address. |
mask | IP mask. |
Disabled
Router configuration
Multiple area router configuration commands specifying the range option can be configured. Thus, OSPF can summarize addresses for many different sets of address ranges.
The following example specifies one summary route to be advertised by the area border router to other areas for all subnets on network 36.0.0.0 and for all hosts on network 192.42.110.0:
interface ethernet 0
ip address 192.42.110.201 255.255.255.0
!
interface ethernet 1
ip address 36.56.0.201 255.255.0.0
!
router ospf 201
network 36.0.0.0 0.255.255.255 area 36.0.0.0
network 192.42.110.0 0.0.0.255 area 0
area 36.0.0.0 range 36.0.0.0 255.0.0.0
area 0 range 192.42.110.0 255.255.255.0
area-id | Identifier for the stub area. The identifier can be either a decimal value or an IP address. |
No stub area is defined.
Router configuration
This command must be configured on all routers in the stub area. Use the area router configuration command with the default-cost option to specify the cost of a default internal router sent into a stub area by an area border router.
There are two stub area router configuration commands: the stub and default-cost options of the area router configuration command. In all routers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an area border router attached to the stub area. The default-cost option provides the metric for the summary default route generated by the area border router into the stub area.
The following example assigns a default cost of 20 to stub network 36.0.0.0:
interface ethernet 0
ip address 36.56.0.201 255.255.0.0
!
router ospf 201
network 36.0.0.0 0.255.255.255 area 36.0.0.0
area 36.0.0.0 stub
area 36.0.0.0 default-cost 20
area authentication
area default-cost
Use the area virtual-link router configuration command with the optional parameters to define an OSPF virtual link. Use the no form of this command to remove the virtual link.
area area-id virtual-link router-id [hello-interval seconds][retransmit-interval seconds]
area-id | Area ID assigned to the transit area for the virtual link. This can be either a decimal value or a valid IP address. There is no default. |
router-id | Router ID associated with the virtual link neighbor. The router ID appears in the show ip ospf display. It is internally derived by each router from the router's interface IP addresses. This value must be entered in the format of an IP address. There is no default. |
hello-interval | (Optional) Number of seconds between the Hello packets that the router sends on an interface. |
seconds | (Optional) Unsigned integer value to be advertised in the router's Hello packets. The value must be the same for all routers attached to a common network. The default is 10 seconds. |
retransmit-interval | (Optional) Number of seconds between link state advertisement retransmissions for adjacencies belonging to the interface. |
seconds | (Optional) Expected round-trip delay between any two routers on the attached network. The value must be greater than the expected round-trip delay. The default is 5 seconds. |
transmit-delay | (Optional) Estimated number of seconds it takes to transmit a link state update packet on the interface. |
seconds | (Optional) Integer value that must be greater than zero. Link state advertisements in the update packet have their age incremented by this amount before transmission. The default value is 1 second. |
dead-interval | (Optional) Number of seconds that a router's Hello packets are not seen before its neighbors declare the router down. |
seconds
| (Optional) Unsigned integer value. The default is four times the Hello interval. As with the Hello interval, this value must be the same for all routers attached to a common network. |
authentication-key | (Optional) Specific password to be used by neighboring routers. |
password | (Optional) Any continuous string of characters that you can enter from the keyboard up to 8 bytes in length. This string acts as a key that will allow the authentication procedure to generate or verify the authentication field in the OSPF header. This key is inserted directly into the OSPF header when originating routing protocol packets. A separate password can be assigned to each network on a per-interface basis. All neighboring routers on the same network must have the same password to be able to route OSPF traffic. There is no default value. The 8 bytes of password are encrypted in the configuration file if the service password-encryption command is enabled. |
See "Syntax Description" for various defaults.
Router configuration
In OSPF, all areas must be connected to a backbone area. If the connection to the backbone is lost, it can be repaired by establishing a virtual link.
The smaller the Hello interval, the faster topological changes will be detected, but more routing traffic will ensue.
The setting of the retransmit interval should be conservative, or needless retransmissions will result. The value should be larger for serial lines and virtual links.
The transmit delay value should take into account the transmission and propagation delays for the interface.
A router will use the specified authentication key only when authentication is enabled for the backbone with the area area-id authentication router configuration command.
Any argument specified after authentication-key password is ignored. Therefore, specify any optional arguments before authentication-key.
The following example establishes a virtual link with default values for all optional parameters:
router ospf 201
network 36.0.0.0 0.255.255.255 area 36.0.0.0
area 36.0.0.0 virtual-link 36.3.4.5
area authentication
Use the area-password router configuration command to configure the IS-IS area authentication password. The no area-password command disables the password.
area-password password
password | Password you assign. |
No area password is defined.
Router configuration
This password is inserted in Level 1 (station router level) link state PDUs (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNP).
The following example assigns an area authentication password:
router isis
area-password angel
domain-password
This command has no arguments or keywords.
Enabled
Router configuration
By default, BGP does not accept subnets redistributed from IGP. To advertise and carry subnet routes in BGP, use an explicit network command or the no auto-summary command. If you disable auto-summarization and have not entered a network command, you will not advertise network routes for networks with subnet routes unless they contain a summary route.
In the following example, network numbers are not summarized automatically:
router bgp 6
no auto-summary
Use the autonomous-system global configuration command to specify the local autonomous system that the router resides in for EGP. To remove the autonomous system number, use the no autonomous-system command.
autonomous-system local-as
local-as | Local autonomous system number to which the router belongs |
No local autonomous system is specified.
Global configuration
Before you can set up EGP routing, you must specify an autonomous system number. The local autonomous system number will be included in EGP messages sent by the router.
The following sample configuration specifies an autonomous system number of 110:
autonomous-system 110
router egp
Use the bgp default local-preference command to change the default local preference value of 100. The no form of the command reverts to the default setting.
bgp default local-preference value
value | Local preference value. Higher is more preferred. Integer from 0 through 4294967295. |
Local preference value of 100
Router configuration
Generally, the default value of 100 allows you to easily define a particular path as less preferable than paths with no local preference attribute. The preference is sent to all routers in the local autonomous system.
In the following example, the default local preference value is raised from the default of 100 to 200:
router bgp 200
bgp default local-preference 200
set local-preference
Use the bgp fast-external-fallover router configuration command to immediately reset the BGP sessions of any directly adjacent external peers if the link used to reach them goes down. Use the no form of this command to disable this feature.
bgp fast-external-falloverThis command has no arguments or keywords.
Enabled
Router configuration
In the following example, the automatic resetting of BGP sessions is disabled:
router bgp 109
no bgp fast-external-fallover
Use the clear arp-cache EXEC command to remove all dynamic entries from the ARP cache and to clear the fast-switching cache.
clear arp-cacheThis command has no arguments or keywords.
EXEC
The following example removes all dynamic entries from the ARP cache and clears the fast-switching cache:
clear arp-cache
To reset a BGP connection, use the clear ip bgp EXEC command at the system prompt.
clear ip bgp {* | address}
* | Resets all current BGP sessions. |
address | Resets only the identified BGP neighbor. |
EXEC
Use this command whenever any of the following changes occur:
The following example shows how to reset all current BGP sessions:
clear ip bgp *
show ip bgp
timers bgp
Use the clear ip route EXEC command to remove one or more routes from the IP routing table.
clear ip route {network [mask] | *}
network | Network or subnet address to remove. |
mask | (Optional) Network mask associated with the IP address you wish to remove. |
* | Removes all entries. |
EXEC
The following example removes a route to network 132.5.0.0 from the IP routing table:
clear ip route 132.5.0.0
show ip route
Use the default-information allowed router configuration command to control exterior information between IGRP processes. The no default-information allowed in command causes IGRP exterior or default routes to be suppressed when received by an IGRP process. The no default-information allowed out command causes IGRP exterior routes to be suppressed in updates.
default-information allowed {in | out}
in | Allows IGRP exterior or default routes to be received by an IGRP process. |
out | Allows IGRP exterior routes to be advertised in updates. |
Normally, exterior routes are always accepted and default information is passed between IGRP processes when doing redistribution.
Router configuration
The default network of 0.0.0.0 used by RIP cannot be redistributed by IGRP.
The following example allows IGRP exterior or default routes to be received by the IGRP process in autonomous system 23:
router igrp 23
default-information allowed in
Use the default-information originate router configuration command to allow the redistribution of network 0.0.0.0 into BGP.
default-information originateThis command has no arguments or keywords.
Disabled
Router configuration
The same functionality will result from the network 0.0.0.0 command, using the network router configuration command.
The following example configures BGP to redistribute network 0.0.0.0 into BGP:
router bgp 164
default-information originate
Use the default-information originate router configuration command to explicitly configure EGP to generate a default route. The no default-information originate command disables this function.
default-information originateThis command has no arguments or keywords.
Disabled
Router configuration
Because EGP can use network 0.0.0.0 as a default route, EGP must be explicitly configured to generate a default route. If the next hop for the default route can be advertised as a third party, it will be included as a third party.
The following example configures EGP to generate a default route:
autonomous system 109
router egp 164
network 131.108.0.0
network 192.31.7.0
neighbor 10.2.0.2
default-information originate
Use the default-information originate router configuration command to generate a default route into an OSPF or IS-IS routing domain. The no default-information originate command disables generation of a default route into the specified OSPF or IS-IS routing domain.
default-information originate [always] [metric metric-value] [metric-type type-value]
originate | For OSPF, causes the router to generate a default external route into an OSPF domain if the router already has a default route and you want to propagate to other routers. For IS-IS, originates the default route whether or not it resides in the routing table. |
always | (Optional) For OSPF, the default route always will be advertised whether or not the router has a default route. |
metric metric-value | (Optional) Metric used for generating the default route. If a value is not specified for this option, and no value is specified using the default-metric router configuration command, the default metric value is 10. The value used is specific to the protocol. |
metric-type type-value | (Optional) For OSPF, the external link type associated with the default route advertised into the OSPF routing domain. It can be one of two values: 1---Type 1 external route 2---Type 2 external route If a metric-type is not specified, the router adopts a Type 2 external route. For IS-IS, it can be one of two values: internal---IS-IS metric which is < 63. external---IS-IS metric which is > 64 < 128. The default is internal. |
level-1 | For IS-IS only, Level 1 routes are redistributed into other IP routing protocols independently. It specifies if IS-IS advertises network 0.0.0.0 into the Level 1 area. |
level-1-2 | For IS-IS only, both Level 1 and Level 2 routes are redistributed into other IP routing protocols. It specifies if IS-IS advertises network 0.0.0.0 into both levels in a single command. |
level-2 | For IS-IS only, Level 2 routes are redistributed into other IP routing protocols independently. It specifies if IS-IS advertises network 0.0.0.0 into the Level 2 subdomain. |
route-map map-name | (Optional) Routing process will generate the default route if the route-map is satisfied. |
Disabled
Router configuration
Whenever you use the redistribute or the default-information router configuration commands to redistribute routes into an OSPF routing domain, the router automatically becomes an autonomous system boundary router. However, an autonomous system boundary router does not, by default, generate a default route into the OSPF routing domain. The router still needs to have a default route for itself before it generates one, except when you have specified the always keyword.
When you use this command for the OSPF process, the default network must reside in the routing table and you must satisfy the route-map map-name keyword. Use the default-information originate always route-map map-name form of the command when you do not want the dependency on the default network in the routing table.
If a router configured with this command has a route to 0.0.0.0 in the routing table, IS-IS will originate an advertisement for 0.0.0.0 in its LSPs.
In the following configuration, the router is forced to generate a default external route into an
IS-IS domain:
router isis
! BGP routes will be distributed into IS-IS
redistribute bgp 120
! access list 2 is applied to outgoing routing updates
distribute-list 2 out
! metric of 60 is specified for default router redistributed into IS-IS
! routing domain.
default-information originate metric 60
! access list 2 defined as giving access to network 100.105.0.0
access-list 2 permit 100.105.0.0 0.0.255.255
The following example specifies a metric of 100 for the default route redistributed into the OSPF routing domain and an external metric type of Type 1:
router ospf 109
redistribute igrp 108 metric 100 subnets
default-information originate metric 100 metric-type 1
isis metric
redistribute
Use the default-metric router configuration command to set default metric values for the RIP, EGP, IGRP, enhanced IGRP, and BGP routing protocols. Use the no default-metric command to remove the metric value and return to the default state.
default-metric number
number | Default metric value appropriate for the specified routing protocol |
Built-in, automatic metric translations, as appropriate for each routing protocol
Router configuration
This command is used in conjunction with the redistribute router configuration command to cause the current routing protocol to use the same metric value for all redistributed routes. A default metric helps solve the problem of redistributing routes with incompatible metrics. Whenever metrics do not convert, using a default metric provides a reasonable substitute and enables the redistribution to proceed.
In BGP, this sets the MULTI_EXIT_DISC metric. (The name of this metric for BGP Versions 2 and 3 is INTER_AS.)
The following example shows a router in autonomous system 109 using both the RIP and the IGRP routing protocols. The example advertises IGRP-derived routes using the RIP protocol and assigns the IGRP-derived routes a RIP metric of 10.
router rip
default-metric 10
redistribute igrp 109
redistribute
Use this form of the default-metric router configuration command to set metrics for IGRP. Use the no default-metric command to remove the metric value and return to the default state.
default-metric bandwidth delay reliability loading mtu
bandwidth | Minimum bandwidth of the route in kilobits per second |
delay | Route delay in tens of microseconds |
reliability | Likelihood of successful packet transmission expressed as a number between 0 and 255 (255 is 100 percent reliability) |
loading | Effective bandwidth of the route expressed as a number between 0 and 255 (255 is 100 percent loading) |
mtu | Minimum Maximum Transmission Unit (MTU) size for the route |
Built-in, automatic metric translations
Router configuration
IGRP metric defaults have been carefully set to work for a wide variety of networks. Take great care in changing these values.
Automatic metric translations for IGRP are only supported when redistributing from IGRP or static.
The following example takes redistributed RIP metrics and translates them into IGRP metrics with values as follows: bandwidth = 1000, delay = 100, reliability = 250, loading = 100, and mtu =1500.
router igrp 109
network 131.108.0.0
redistribute rip
default-metric 1000 100 250 100 1500
redistribute
Use the distance router configuration command to define an administrative distance. Use the no distance command with the appropriate arguments to remove a distance definition.
distance weight [address mask [access-list-number]] [ip]
weight | Integer from 10 to 255 for the administrative distance. (Values 0 through 9 are reserved for internal use.) Used alone, the argument specifies a default administrative distance that the router uses when no other specification exists for a routing information source. A distance of 255 is the maximum possible distance, and any route with that distance will not be installed in the routing table. |
address | (Optional) IP address. |
mask | (Optional) In dotted-decimal format which bits, if any, to ignore in the address value; a set bit in the mask argument instructs the router to ignore the corresponding bit in the address value. |
access-list-number | (Optional) Number of a standard IP access list to be applied to incoming routing updates. |
ip | (Optional) IP-derived routes for IS-IS. Can be applied independently for IP routes and ISO CLNS routes. |
See values in Table 17-1.
Router configuration
Numerically, an administrative distance is an integer between 0 and 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored.
When the optional access list number is used with this command, it is applied when a network is being inserted into the routing table. This allows filtering of networks according to the IP address of the router supplying the routing information. This could be used, as an example, to filter out possibly incorrect routing information from routers not under your administrative control.
The order in which you enter distance commands can affect the assigned administrative distances in unexpected ways (see "Example" for further clarification).
Weight values are also subjective; there is no quantitative method for choosing weight values.
For BGP, the distance command sets the administrative distance of the External BGP route.
Default administrative distances are shown in Table 17-1.
| Route Source | Default Distance |
|---|---|
Connected interface | 0 |
Static route | 1 |
External BGP | 20 |
IGRP | 100 |
OSPF | 110 |
IS-IS | 115 |
RIP | 120 |
EGP | 140 |
Internal BGP | 200 |
Unknown | 255 |
The show ip protocols EXEC command displays the default administrative distance for a specified routing process.
In the following example, the router igrp global configuration command sets up IGRP routing in autonomous system number 109. The network router configuration commands specify IGRP routing on networks 192.31.7.0 and 128.88.0.0. The first distance router configuration command sets the default administrative distance to 255, which instructs the router to ignore all routing updates from routers for which an explicit distance has not been set. The second distance command sets the administrative distance for all routers on the Class C network 192.31.7.0 to 90. The third distance command sets the administrative distance for the router with the address 128.88.1.3 to 120.
router igrp 109
network 192.31.7.0
network 128.88.0.0
distance 255
distance 90 192.31.7.0 0.0.0.255
distance 120 128.88.1.3 0.0.0.0
distance bgp
Use the distance bgp router configuration command to allow the use of three possible administrative distances---external, internal, and local---that could be a better route to a node. Use the no distance bgp command to reset these values to their defaults.
distance bgp external-distance internal-distance local-distance
external-distance | Administrative distance for BGP external routes. External routes are routes for which the best path is learned from a neighbor external to the autonomous system. Acceptable values are from 1 to 255. A distance of 255 is the maximum possible distance, and any route with that distance will not be installed in the routing table. |
internal-distance | Administrative distance for BGP internal routes. Internal routes are those routes that are learned from another BGP entity within the same autonomous system. Acceptable values are from 1 to 255. A distance of 255 is the maximum possible distance, and any route with that distance will not be installed in the routing table. |
local-distance | Administrative distance for BGP local routes. Local routes are those networks listed with a network router configuration command, often as back doors, for that router or for networks that are being redistributed from another process. Acceptable values are from 1 to 255. A distance of 255 is the maximum possible distance, and any route with that distance will not be installed in the routing table. |
external-distance = 20
internal-distance = 200
local-distance = 200
Router configuration
An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. Numerically, an administrative distance is an integer between 0 and 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored.
Use this command if another protocol is known to be able to provide a better route to a node than was actually learned via external BGP, or if some internal routes should really be preferred by BGP.
In the following example, internal routes are known to be preferable to those learned through the IGP, so the administrative distance values are set accordingly:
router bgp 109
network 131.108.0.0
neighbor 129.140.6.6 remote-as 123
neighbor 128.125.1.1 remote-as 47
distance bgp 20 20 200
distance
Use the distribute-list in router configuration command to filter networks received in updates. (Not supported in IS-IS.) Use the no form of this command to disable this function.
distribute-list access-list-number in [interface-name]
access-list-number | Standard IP access list number. The list explicitly specifies which networks are to be received and which are to be suppressed. |
interface-name | (Optional) Interface on which the access list should be applied to incoming updates. If no interface is specified, the access list will be applied to all incoming updates. |
Disabled
Router configuration
The following example causes only two networks to be accepted by a RIP routing process: network 0.0.0.0 (the RIP default) and network 131.108.0.0.
access-list 1 permit 0.0.0.0
access-list 1 permit 131.108.0.0
access-list 1 deny 0.0.0.0 255.255.255.255
router rip
network 131.108.0.0
distribute-list 1 in
A dagger () indicates that the command is documented in another chapter.
access-list
distribute-list out
redistribute
Use the distribute-list out router configuration command to suppress networks from being advertised in updates. Use the no form of this command to disable this function.
distribute-list access-list-number out {interface-name | routing-process}
access-list-number | Standard IP access list number. The list explicitly specifies which networks are to be sent and which are to be suppressed in routing updates. |
interface-name | Name of a particular interface. Does not apply to OSPF. |
routing-process | Name of a particular routing process, or static or connected. |
Disabled
Router configuration
When redistributing networks, a routing process name can be specified as an optional trailing argument to the distribute-list command. This causes the access list to be applied to only those routes derived from the specified routing process. After the process-specific access list is applied, any access list specified by a distribute-list command without a process name argument will be applied. Addresses not specified in the distribute-list command will not be advertised in outgoing routing updates.
The following example would cause only one network to be advertised by a RIP routing process: network 131.108.0.0.
access-list 1 permit 131.108.0.0
access-list 1 deny 0.0.0.0 255.255.255.255
router rip
network 131.108.0.0
distribute-list 1 out
In the following example, access list 1 is applied to outgoing routing updates and IS-IS is enabled on interface Ethernet 0. Only network 131.131.101.0 will be advertised in outgoing IS-IS routing updates.
router isis
redistribute ospf 109
distribute-list 1 out
interface Ethernet 0
ip router isis
access-list 1 permit 131.131.101.0 0.0.0.255
A dagger () indicates that the command is documented in another chapter.
access-list
distribute-list in
redistribute
Use the domain-password router configuration command to configure the IS-IS routing domain authentication password. The no domain-password command disables the password.
domain-password password
password | Password you assign |
No password is specified.
Router configuration
This password is inserted in Level 2 (area router level) link state PDUs (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNP).
The following example assigns an authentication password to the routing domain:
router isis
domain-password flower
area-password
Use the ip address interface configuration command to specify the IP address on an interface. The no ip address command removes the specified secondary address.
ip address address mask [secondary]
address | IP address |
mask | IP address mask |
secondary | (Optional) Address to be added as a secondary address |
Disabled
Interface configuration
The optional keyword secondary allows an unlimited number of secondary addresses to be specified. Secondary addresses are treated like primary addresses, except that the system never generates datagrams other than routing updates with secondary source addresses. IP broadcasts and ARP requests are handled properly, as are interface routes in the IP routing table.
Secondary IP addresses can be used in a variety of situations. The following are the most common applications:
The following example specifies 131.108.1.27 as the primary address and 192.31.7.17 as a secondary address for interface Ethernet 0:
interface ethernet 0
ip address 131.108.1.27 255.255.255.0
ip address 192.31.7.17 255.255.255.0 secondary
Use the ip as-path access-list global configuration command to define a BGP-related access list. To disable use of the access list, use the no ip as-path access-list command.
ip as-path access-list access-list-number {permit | deny} as-regular-expression
access-list-number | Integer from 1 to 199 that indicates the regular expression access list number. |
permit | Permits access for matching conditions. |
deny | Denies access to matching conditions. |
as-regular-expression | Autonomous system in the access list using a regular expression. See the "Regular Expressions" appendix for information on forming regular expressions. |
No access lists are defined.
Global configuration
You can specify an access list filter on both inbound and outbound BGP routes. In addition, you can assign weights based on a set of filters. Each filter is an access list based on regular expressions. If the regular expression matches the representation of the autonomous system path of the route as an ASCII string, then the permit or deny condition applies. The autonomous system path does not contain the local autonomous system number. Use the ip as-path access-list global configuration command to define an BGP access list, and the neighbor router configuration command to apply a specific access list.
See the "Regular Expressions" appendix for information on forming regular expressions.
The following example specifies that the BGP neighbor with IP address 128.125.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 123.
ip as-path access-list 1 deny _123_
ip as-path access-list 1 deny ^123 .*
! The space in the above expression (^123.*) is required.
router bgp 109
network 131.108.0.0
neighbor 129.140.6.6 remote-as 123
neighbor 128.125.1.1 remote-as 47
neighbor 128.125.1.1 filter-list 1 out
neighbor distribute-list
neighbor filter-list
Use the ip default-network global configuration command to select a network as a candidate route for computing the gateway of last resort. Use the no default-network command to remove the route.
ip default-network network-number
network-number | Number of the network |
If the router has a directly connected interface onto the specified network, the dynamic routing protocols running on that router will generate (or source) a default route. For RIP, this is flagged as the pseudonetwork 0.0.0.0; for IGRP, it is the network itself, flagged as an exterior route.
Global configuration
The router uses both administrative distance and metric information to determine the default route. Multiple ip default-network commands can be given. All candidate default routes, both static (that is, flagged by ip default-network) and dynamic, appear in the routing table preceded by an asterisk.
If the IP routing table indicates that the specified network number is subnetted and a non-zero subnet number is specified, then the system will automatically configure a static summary route. This static summary route is configured instead of a default network. The effect of the static summary route is to cause traffic destined for subnets that are not explicitly listed in the IP routing table to be routed using the specifed subnet.
The following example defines a static route to network 10.0.0.0 as the static default route:
ip route 10.0.0.0 255.0.0.0 131.108.3.4
ip default-network 10.0.0.0
ip default-network 129.140.0.0
show ip route
Use the ip gdp interface configuration command to enable GDP routing on an interface. The no ip gdp command disables GDP routing, with all default parameters.
ip gdp [priority number | reporttime seconds | holdtime seconds]
priority number | (Optional) Alters the GDP priority; default is a priority of 100. A larger number indicates a higher priority. |
reporttime seconds | (Optional) Alters the GDP reporting interval; the default is 5 seconds for broadcast media such as Ethernets, and never for nonbroadcast media such as X.25. |
holdtime seconds | (Optional) Alters the GDP default hold time of 15 seconds. |
priority = 100
reporttime = 5 seconds for broadcast media; 0 for nonbroadcast media
holdtime = 15 seconds
Interface configuration
When enabled on an interface, GDP updates report the primary and secondary IP addresses of that interface.
In the following example, GDP is enabled on interface Ethernet 1 with a report time of 10 seconds, and priority and hold time set to their defaults (because none are specified):
ip gdp reporttime 10
Use the ip irdp interface configuration command to enable ICMP Router Discovery Protocol (IRDP) processing on an interface. The no ip irdp command disables IRDP routing on the specified interface.
ip irdp [multicast | holdtime seconds | maxadvertinterval seconds | minadvertinterval
multicast | (Optional) Use the multicast address (224.0.0.1) instead of IP broadcasts. |
holdtime seconds | (Optional) Length of time in seconds advertisements are held valid. Default is three times the maxadvertinterval value. Must be greater than maxadvertinterval and cannot be greater than 9000 seconds. |
maxadvertinterval seconds | (Optional) Maximum interval in seconds between advertisements. The default is 600 seconds. |
minadvertinterval seconds | (Optional) Minimum interval in seconds between advertisements. The default is 0.75 times the maxadvertinterval. If you change the maxadvertinterval value, this value defaults to three-quarters of the new value. |
preference number | (Optional) Router's preference value. The allowed range is -231 to 231. The default is 0. A higher value increases the router's preference level. You can modify a particular router so that it will be the preferred router to which others home. |
address address [number] | (Optional) IP address (address) to proxy-advertise, and optionally, its preference value (number). |
Disabled.
When enabled, IRDP uses these defaults:
Interface configuration
If you change maxadvertinterval, the other two values also change, so it is important to change maxadvertinterval first before changing either holdtime or minadvertinterval.
The following example illustrates how to set the various IRDP processes:
! enable irdp on interface Ethernet 0
interface ethernet 0
ip irdp
! send IRDP advertisements to the multicast address
ip irdp multicast
! increase router preference from 100 to 50
ip irdp preference 50
! set maximum time between advertisements to 400 secs
ip irdp maxadvertinterval 400
! set minimum time between advertisements to 100 secs
ip irdp minadvertinterval 100
! advertisements are good for 6000 seconds
ip irdp holdtime 6000
! proxy-advertise 131.108.14.5 with default router preference
ip irdp address 131.108.14.5
! proxy-advertise 131.108.14.6 with preference of 50
ip irdp address 131.108.14.6 50
Use the ip ospf authentication-key interface configuration command to assign a password to be used by neighboring routers that are using OSPF's simple password authentication. The no ip ospf authentication-key command removes any previously assigned OSPF password.
ip ospf authentication-key password
password | Any continuous string of characters that can be entered from the keyboard up to 8 bytes in length. |
No password is specified.
Interface configuration
The password created by this command is used as a "key" that is inserted directly into the OSPF header when the router originates routing protocol packets. A separate password can be assigned to each network on a per-interface basis. All neighboring routers on the same network must have the same password to be able to exchange OSPF information.
In the following example, the authentication key is enabled with the string yourpass:
ip ospf authentication-key yourpass
area authentication
Use the ip ospf cost interface configuration command to explicitly specify the cost of sending a packet on an interface. The no ip ospf cost command resets the path cost for an interface to the default value.
ip ospf cost cost
cost | Unsigned integer value expressed as the link state metric. The range is from 1 to 65535. |
See "Usage Guidelines"
Interface configuration
Unlike IGRP, you must set this metric manually using this command, if you need to change the default. Changing the bandwidth does not change the link cost.
The link state metric is advertised as the link cost in the router's router link advertisement. We do not support Type of Service (TOS), so you can assign only one cost per interface.
In general, the path cost is calculated as follows:
108 ÷ Bandwidth
Using the above formula, the default path costs were calculated as noted in the following list. If these values do not suit your network, you can use your own method of calculating path costs.
The following example sets the interface cost value to 65:
ip ospf cost 65
Use the ip ospf dead-interval interface configuration command to set the number of seconds that a router's Hello packets must not have been seen before its neighbors declare the router down. The no ip ospf dead-interval command resets the length of time to the default value.
ip ospf dead-interval seconds
seconds | Unsigned integer that specifies the interval in seconds; the value must be the same for all nodes on the network. |
Four times the interval set for the ip ospf hello-interval command
Interface configuration
The interval is advertised in the router's Hello packets. This value must be the same for all routers on a specific network.
The following example sets the OSPF dead interval to 60 seconds:
interface ethernet 1
ip ospf dead-interval 60
ip ospf hello-interval
Use the ip ospf hello-interval interface configuration command to specify the interval between Hello packets that the router sends on the interface. The no ip ospf hello-interval command resets the interval to the default value.
ip ospf hello-interval seconds
seconds | Unsigned integer that specifies the interval in seconds. The value must be the same for all nodes on a specific network. |
10 seconds
Interface configuration
This value is advertised in the router's Hello packets. The smaller the Hello interval, the faster topological changes will be detected, but more routing traffic will ensue. This value must be the same for all routers on a specific network.
The following example sets the interval between Hello packets to 15 seconds:
interface ethernet 1
ip ospf hello-interval 15
ip ospf dead-interval
Use the ip ospf-name-lookup global configuration command to configure OSPF to look up Domain Name System (DNS) names for use in all OSPF show EXEC command displays. The
no ip ospf-name-lookup command disables the feature.
This command has no arguments or keywords.
Disabled
Global configuration
This feature makes it easier to identify a router because it is displayed by name rather than by its router ID or neighbor ID.
The following example configures OSPF to look up DNS names for use in all OSPF show EXEC command displays:
ip ospf-name-lookup
The following is sample output of the show ip ospf database EXEC command, for example, once you have enabled the DNS name lookup feature.
Router# show ip ospf database
OSPF Router with id (160.89.41.1) (Autonomous system 109)
Router Link States (Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum Link count
160.89.41.1 router 381 0x80000003 0x93BB 4
160.89.34.2 neon 380 0x80000003 0xD5C8 2
Net Link States (Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum
160.89.32.1 router 381 0x80000001 0xC117
Use the ip ospf network interface configuration command to configure the OSPF network type to a type other than the default for a given media. The no ip ospf network command restores the default.
ip ospf network {broadcast | non-broadcast}
broadcast | Sets the network type to broadcast. |
non-broadcast | Sets the network type to nonbroadcast. |
Depends on the network type
Interface configuration
Using this feature, you can configure broadcast networks as nonbroadcast multiaccess networks when, for example, you have routers in your network that do not support multicast addressing. You can also configure nonbroadcast multiaccess networks, such as X.25, Frame Relay, and SMDS, as broadcast networks. This feature saves you from having to configure neighbors.
If this command is issued on an interface that does not allow it, it will be ignored.
The following example sets your OSPF network as a broadcast network:
interface serial 0
ip address 160.89.77.17 255.255.255.0
ip ospf network broadcast
encapsulation frame-relay
neighbor (OSPF)
x25-map
frame-relay map
Use the ip ospf priority interface configuration command to set the router's priority, which helps determine the designated router for this network. The no ip ospf priority command resets the router priority to the default value.
ip ospf priority number
number | 8-bit unsigned integer that specifies the priority. The range is from 0 to 255. |
Priority of 1
Interface configuration
When two routers attached to a network both attempt to become the designated router; the one with the higher router priority takes precedence. If there is a tie, the router with the higher router ID takes precedence. A router with a router priority set to zero is ineligible to become the designated router or backup designated router. Router priority is only configured for interfaces to multiaccess networks (in other words, not point-to-point networks).
This priority value is used when you configure OSPF for nonbroadcast networks using the neighbor router configuration command for OSPF.
The following example sets the router priority value to 4:
interface ethernet 0
ip ospf priority 4
ip ospf network
neighbor (OSPF)
To specify the number of seconds between link state advertisement retransmissions for adjacencies belonging to the interface, use the ip ospf retransmit-interval interface configuration command. The no ip ospf retransmit-interval command resets the link state advertisement retransmission interval to the default value.
ip ospf retransmit-interval seconds
seconds | Number of seconds between retransmissions; it must be greater than the expected round-trip delay between any two routers on the attached network. The range is 1 to 65535 seconds. The default is 5 seconds. |
5 seconds
Interface configuration
When a router sends a link state advertisement (LSA) to its neighbor, it keeps the LSA until it receives back the acknowledgment. If it receives no acknowledgment in seconds, it will retransmit the LSA.
The setting of this parameter should be conservative, or needless retransmission will result. The value should be larger for serial lines and virtual links.
The following example sets the retransmit-interval value to 8 seconds:
interface ethernet 2
ip ospf retransmit-interval 8
Use the ip ospf transmit-delay interface configuration command to set the estimated number of seconds it takes to transmit a link state update packet on the interface. The no ip ospf transmit-delay command resets the estimated transmission time to the default value.
ip ospf transmit-delay seconds
seconds | Integer that specifies the number of seconds it takes to transmit a link state update. The range is 1 to 65535 seconds. |
1 second
Interface configuration
Link state advertisements in the update packet must have their age incremented by the amount specified in the seconds argument before transmission. The value assigned should take into account the transmission and propagation delays for the interface.
If the delay is not added before transmission over a link, the time in which the LSA propagates over the link is not considered. This setting has more significance on very low speed links.
The following example sets the retransmit-delay value to 3 seconds:
interface ethernet 0
ip ospf transmit-delay 3
Use the ip route global configuration command to establish static routes. The no ip route command removes the static routes.
ip route network [mask] {address | interface} [distance]
network | Internet address of the target network or subnet |
mask | (Optional) Network mask that lets you mask network and subnetwork bits |
address | Internet address of the next hop that can be used to reach that network |
interface | Network interface to use |
distance | (Optional) An administrative distance |
No static routes are established.
Global configuration
A static route is appropriate when the router cannot dynamically build a route to the destination.
If you specify an administrative distance, you are flagging a static route that can be overridden by dynamic information. For example, IGRP-derived routes have a default administrative distance of 100. To have a static route that would be overridden by an IGRP dynamic route, specify an administrative distance greater than 100. Static routes have a default administrative distance of 1.
Static routes that point to an interface will be advertised via RIP, IGRP, and other dynamic routing protocols, regardless of whether redistribute static commands were specified for those routing protocols. This is because static routes that point to an interface are considered in the routing table to be connected and hence lose their static nature. However, if you define a static route to an interface that is not one of the networks defined in a network command, no dynamic routing protocols will advertise the route unless a redistribute static command is specified for these protocols.
In the following example, an administrative distance of 110 was chosen. In this case, packets for network 10.0.0.0 will be routed through to the router at 131.108.3.4 if dynamic information with administrative distance less than 110 is not available.
ip route 10.0.0.0 255.0.0.0 131.108.3.4 110
In the following example, packets for network 131.108.0.0 will be routed to the router at 131.108.6.6:
ip route 131.108.0.0 255.255.0.0 131.108.6.6
Use the ip router isis interface configuration command to configure an IS-IS routing process for IP over a specified interface. The no ip router isis command disables IS-IS for IP on the interface.
ip router isis [tag]
tag | (Optional) Defines a meaningful name for a routing process. If not specified, a null tag is assumed. It must be unique among all IP router processes for a given router. Use the same text for the argument tag as specified in the router isis global configuration command. |
No routing processes are specified.
Interface configuration
The following example specifies IS-IS as an IP routing protocol for a process named Finance, and specifies that the Finance process will be routed on interfaces Ethernet 0 and serial 0:
router isis Finance
interface Ethernet 0
ip router isis Finance
interface serial 0
ip router isis Finance
router isis
Use the ip split-horizon interface configuration command to enable the split-horizon mechanism. The no ip split-horizon command turns off the split-horizon mechanism.
ip split-horizonThis command has no arguments or keywords.
Varies with media
Interface configuration
For all interfaces except those for which either Frame Relay or SMDS encapsulation is enabled, the default condition for this command is ip split-horizon; in other words, the split horizon feature is active. If the interface configuration includes either the encapsulation frame-relay or encapsulation smds interface configuration commands, then the default is for split horizon to be disabled. Split horizon is not disabled by default for interfaces using any of the X.25 encapsulations.
If split horizon has been disabled on an interface and you wish to enable it, use the ip split-horizon command to restore the split horizon mechanism.
The following example illustrates a simple example of disabling split horizon on a serial link. In this example, the serial link is connected to an X.25 network:
interface serial 0
encapsulation x25
no ip split-horizon
Use the is-type router configuration command to configure the IS-IS level at which the router will operate. The no is-type command resets the parameter to the default.
is-type {level-1 | level-1-2 | level-2-only}
level-1 | Router acts as a station router. |
level-1-2 | Router acts as both a station router and an area router. |
level-2-only | Router acts as an area router only. |
Router acts as both a station router and an area router.
Router configuration
The following example specifies an area router:
router isis
is-type level-2-only
Use the isis circuit-type interface configuration command to configure the type of adjacency desired for the specified interface. The no isis circuit-type command resets the circuit type to Level l and Level 2.
isis circuit-type {level-1 | level-1-2 | level-2-only}
level-1 | A Level 1 adjacency may be established if there is at least one area address in common between this system and its neighbors. |
level-1-2 | A Level 1 and Level 2 adjacency is established if the neighbor is also configured as level-1-2 and there is at least one area in common. If there is no area in common, a Level 2 adjacency is established. This is the default. |
level-2-only | A Level 2 adjacency is established if and only if the neighbor is configured exclusively to be a Level 2 router. |
A Level 1 and Level 2 adjacency is established.
Interface configuration
In the following example, a router is configured to require Level 1 adjacency if there is at least one area address in common between this system and its neighbors:
ip router isis
interface serial 0
isis circuit-type level-1
Use the isis csnp-interval interface configuration command to configure the IS-IS complete sequence number PDUs (CSNP) interval for the specified interface. The no isis csnp-interval command restores the default value.
isis csnp-interval seconds {level-1 | level-2}
seconds | Interval of time between transmission of CSNPs on multiaccess networks. This interval only applies for the designated router. The default is 10 seconds. |
level-1 | Configures the interval of time between transmission of CSNPs for Level 1 independently. |
level-2 | Configures the interval of time between transmission of CSNPs for Level 2 independently. |
10 seconds
Interface configuration
This command only applies for the designated router (DR) for a specified interface. Only DRs send CSNP packets in order to maintain database synchronization. The CSNP interval can be configured independently for Level 1 and Level 2. This feature does not apply to serial point-to-point interfaces. It does apply to WAN connections if the WAN is viewed as a multiaccess meshed network.
In the following example, interface serial 0 is configured for transmitting CSN PDUs every 5 seconds. The router is configured to act as a station router.
interface serial 0
isis csnp-interval 5 level-1
Use the isis hello-interval interface configuration command to specify the length of time, in seconds, between Hello packets that the router sends on the specified interface. The no isis hello-interval command restores the default value.
isis hello-interval seconds {level-1 | level-2}
seconds | Unsigned integer value. A value three times the Hello interval seconds is advertised as the holdtime in the Hello packets transmitted. It must be the same for all routers attached to a common network. With smaller Hello intervals, topological changes are detected faster, but there is more routing traffic. The default is 10 seconds. |
level-1 | Configures the Hello interval for Level 1 independently. Use this on X.25, SMDS, and Frame Relay multiaccess networks. |
level-2 | Configures the Hello interval for Level 2 independently. Use this on X.25, SMDS, and Frame Relay multiaccess networks. |
10 seconds
Interface configuration
The Hello interval can be configured independently for Level 1 and Level 2, except on serial point-to-point interfaces. (Because there is only a single type of Hello packet sent on serial links, it is independent of Level 1 or Level 2.) The level-1 and level-2 keywords are used on X.25, SMDS, and Frame Relay multiaccess networks.
In the following example, interface serial 0 is configured to advertise Hello packets every 5 seconds. The router is configured to act as a station router. This will cause more traffic than configuring a longer interval, but topological changes will be detected faster.
interface serial 0
isis hello-interval 5 level-1
Use the isis metric interface configuration command to configure the metric (or cost) for the specified interface. The no isis metric command restores the default metric value.
isis metric default-metric [delay-metric [expense-metric [error-metric]]] {level-1 | level-2}
default-metric | Metric used for the redistributed route. The default metric is used as a value for the IS-IS metric. This is the value assigned when there is no QOS routing performed. Only this metric is supported by Cisco routers. You can configure this metric for Level 1 and/or Level 2 routing. The range is from 0 to 63. The default value is 10. |
delay-metric | Not supported. |
expense-metric | Not supported. |
error-metric | Not supported. |
level-1 | Router acts as a station router (Level 1) only. |
level-2 | Router acts as an area router (Level 2) only. |
default-metric = 10
Interface configuration
Specifying the level-1 or level-2 keywords resets the metric only for Level 1 or Level 2 routing, respectively.
In the following example, interface serial 0 is configured for a default link-state metric cost of 15 for Level 1:
interface serial 0
isis metric 15 level-1
default-information
redistribute
Use the isis password interface configuration command to configure the authentication password for a specified interface. The no isis password command disables authentication for IS-IS.
isis password password {level-1 | level-2}
password | Authentication password you assign for an interface. |
level-1 | Configures the authentication password for Level 1 independently. For Level 1 routing, the router acts as a station router only. |
level-2 | Configures the authentication password for Level 2 independently. For Level 2 routing, the router acts as an area router only. |
Disabled
Interface configuration
Different passwords can be assigned for different routing levels using the level-1 and level-2 keyword arguments.
Specifying the level-1 or level-2 keywords disables the password only for Level 1 or Level 2 routing, respectively. If no keyword is specified, the default is level-1.
The following example configures a password for interface serial 0 at Level 1:
interface serial 0
isis password frank level-1
Use the isis priority interface configuration command to configure the priority of designated routers. The no isis priority command resets priority to 64.
isis priority value {level-1 | level-2}
value | Sets the priority of a router and is a number from 0 to 127. The default value is 64. |
level-1 | Sets the priority of a router for Level 1 independently. |
level-2 | Sets the priority of a router for Level 2 independently. |
Priority of 64
Interface configuration
Priorities can be configured for Level 1 and Level 2 independently. Specifying the level-1 or
level-2 keywords resets priority only for Level 1 or Level 2 routing, respectively.
The following example shows Level 1 routing given priority by setting the priority level to 50:
interface serial 0
isis priority 50 level-1
Use the isis retransmit-interval interface configuration command to configure the number of seconds between retransmission of IS-IS link-state PDU (LSP) retransmission for point-to-point links. The no isis retransmit-interval command restores the default value.
isis retransmit-interval seconds
seconds | Integer that should be greater than the expected round-trip delay between any two routers on the attached network. The setting of this parameter should be conservative, or needless retransmission will result. The value should be larger for serial lines and virtual links. The default value is 5 seconds. |
5 seconds
Interface configuration
The following example configures interface serial 0 for retransmission of IS-IS LSP every
10 seconds for a large serial line:
interface serial 0
isis retransmit-interval 10
A dagger () indicates that the command is documented in another chapter.
encapsulation ppp
frame-relay keepalive
smds dxi
Use the match as-path route-map configuration command to match a BGP autonomous system path access list. Use the no form of this command to remove the path list entry.
match as-path path-list-number
path-list-number | Autonomous system path access list. An integer from 1 through 199. |
No path lists are defined.
Route-map configuration
The values set by the match and set commands override global values. For example, the weights assigned with the match as-path and set weight route-map commands override the weights assigned using the neighbor weight and neighbor filter-list commands.
A route map can have several parts. Any route that does not match at least one match clause relating to a route- map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want o modify only some data, you must configure second route-map section with an explicit match specified.
The implemented weight is based on the first matched autonomous system path.
In the following example, the AS path is set to match BGP autonomous system path access list 20:
route-map igp2bgp
match as-path 20
route-map
set
Use the match interface route-map configuration command to distribute any routes that have their next hop out one of the interfaces specified. Use the no form of this command to remove the match interface entry.
match interface name unit...name unit
name unit | Names of interfaces, such as Ethernet 0 or Serial 2. |
No match interfaces are defined.
Route-map configuration
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route- map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want o modify only some data, you must configure second route-map section with an explicit match specified.
In the following example, routes that have their next hop out interface Ethernet 0 will be distributed:
route-map name
match interface ethernet 0
route-map
set
Use the match ip address route-map configuration command to distribute any routes that have a destination network number address that is permitted by a standard access list. Use the no form of this command to remove the match ip address entry.
match ip address access-list-number...access-list-number
access-list-number | One or more numeric identifiers of access lists. An integer from 1 through 99. |
No access list numbers are specified.
Route-map configuration
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route- map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want o modify only some data, you must configure second route-map section with an explicit match specified.
In the following example, routes that have addresses specified by access list numbers 5 and 80 will be distributed:
route-map name
match ip address 5 80
route-map
set
Use the match ip next-hop route-map configuration command to redistribute any routes that have a next-hop router address passed by one of the access lists specified. Use the no form of this command to remove the next-hop entry.
match ip next-hop access-list-number...access-list-number
access-list-number | One or more numeric identifiers of standard access lists. An integer from 1 through 99. |
Routes are distributed freely, without being required to match a next-hop address.
Route-map configuration
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route- map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want o modify only some data, you must configure second route-map section with an explicit match specified.
In the following example, routes that have a next-hop router address passed by access list 5 or 80 will be distributed:
route-map name
match ip next-hop 5 80
route-map
set
Use the match ip route-source route-map configuration command for any routes that have been advertised by routers at the address specified by the access lists. Use the no form of this command to remove the route-source entry.
match ip route-source access-list-number...access-list-number
access-list-number | One or more numeric identifiers of access lists. An integer from 1 through 99. |
No filtering on route source.
Route-map configuration
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route- map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want o modify only some data, you must configure second route-map section with an explicit match specified.
There are situations in which a route's next hop and source router address are not the same.
In the following example, routes that have been advertised by routers at the addresses specified by access lists 5 and 80 will be distributed:
route-map name
match ip route-source 5 80
route-map
set
Use the match metric route-map configuration command for any routes with the metric specified. Use the no form of this command to remove the entry.
match metric metric-value
metric-value | Route metric. This may be an IGRP five-part metric. A metric value from 0 through 4294967295. |
No filtering on a metric value.
Route-map configuration
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route- map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want o modify only some data, you must configure second route-map section with an explicit match specified.
In the following example, routes with the metric 5 will be redistributed.
route-map name
match metric 5
route-map
set
Use the match route-type route-map configuration command for any routes that are of the specified type. Use the no form of this command to remove the route-type entry.
match route-type {local | internal | external [type-1 | type-2] | level-1 | level-2}
local | Locally generated BGP routes |
internal | OSPF intra-area and interarea routes or enhanced IGRP internal routes |
external [type-1 | type-2] | OSPF external routes, or enhanced IGRP external routes. For OSPF, external type-1 matches only type 1 external routes and external type-2 matches only type 2 external routes. |
level-1 | IS-IS Level 1 routes |
level-2 | IS-IS Level 2 routes |
Disabled
Route-map configuration
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route- map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure second route-map section with an explicit match specified.
In the following example, internal routes will be redistributed:
route-map name
match route-type internal
route-map
set
Use the match tag command for any routes stored in the routing table with one of the tags specified. Use the no form of this command to remove the tag entry.
match tag tag-value...tag-value
tag-value | List of one or more route tag values. An integer from 0 through 4294967295. |
No match tag values are defined.
Route-map configuration
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route- map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want o modify only some data, you must configure second route-map section with an explicit match specified.
In the following example, routes stored in the routing table with tag 5 will be redistributed:
route-map name
match tag 5
route-map
set
Use the metric holddown router configuration command to keep new IGRP routing information from being used for a certain period of time. Use the no metric holddown command to disable metric holddown.
metric holddownThis command has no arguments or keywords.
Disabled
Router configuration
Holddown keeps new routing information from being used for a certain period of time. This can prevent routing loops caused by slow convergence. It is sometimes advantageous to disable holddown to increase the network's ability to quickly respond to topology changes; this command provides this function.
Use the metric holddown command if other routers within the IGRP autonomous system are not configured with no metric holddown. If all routers are not configured the same way, you increase the possibility of routing loops.
The following example disables metric holddown:
router igrp 15
network 131.108.0.0
network 192.31.7.0
no metric holddown
metric maximum-hops
metric weights
timers basic
Use the metric maximum-hops router configuration command to cause the IP routing software to advertise as unreachable those routes with a hop count higher than is specified by the command (IGRP only). Use the no metric maximum-hops command to reset the value to the default.
metric maximum-hops hops
hops | Maximum hop count (in decimal). The default value is 100 hops; the maximum number of hops that can be specified is 255. |
100 hops
Router configuration
This command provides a safety mechanism that breaks any potential count-to-infinity problems. It causes the IP routing software to advertise as unreachable routes with a hop count greater than the value assigned to the hops argument.
In the following example, a router in autonomous system 71 attached to network 15.0.0.0 wants a maximum hop count of 200, doubling the default. The network administrators decided to do this because they have a complex WAN that can generate a large hop count under normal (nonlooping) operations.
router igrp 71
network 15.0.0.0
metric maximum-hops 200
metric holddown
metric weights
Use the metric weights router configuration command to allow the tuning of the IGRP metric calculations. Use the no metric weights command to reset the values to their defaults.
metric weights tos k1 k2 k3 k4 k5
tos | Type of service. Currently it must always be zero. |
k1-k5 | Constants that convert an IGRP metric vector into a scalar quantity. |
tos=0
k1 = 1
k2 = 0
k3 = 1
k4 = 0
k5 = 0
Router configuration
Use this command to alter the default behavior of IGRP routing and metric computation and allow the tuning of the IGRP metric calculation for a particular type of service (TOS).
If k5 equals 0, the composite IGRP metric is computed according to the following formula:
metric = [k1 * bandwidth + (k2 * bandwidth)/(256 - load) + k3 * delay]
If k5 does not equal zero, an additional operation is done:
metric = metric * [k5 / (reliability + k4)]
Bandwidth is inverse minimum bandwidth of the path in bits per second scaled by a factor of 10*1010. The range is from a 1200 bps line to 10 Gbps.
Delay is in units of 10 microseconds. This gives a range of 10 microseconds to 168 seconds. A delay of all ones indicates that the network is unreachable.
The delay parameter is stored in a 24-bit field, in tens of microseconds. Hence, the delay can be from 1 (10 microseconds) to hex FFFFFF (decimal 16777215), which corresponds to 167.77215 seconds. A delay of all ones (that is, a delay of 16777215) indicates that the network is unreachable.
Table 17-2 lists the default values used for several common media.
| Media Type | Delay | Bandwidth |
|---|---|---|
Satellite | 200,000 (2 sec) | 20 (500 Mbit) |
Ethernet | 100 (1 ms) | 1,000 |
1.544 Mbps | 2000 (20 ms) | 6,476 |
64 kbps | 2000 | 156,250 |
56 kbps | 2000 | 178,571 |
10 kbps | 2000 | 1,000,000 |
1 kbps | 2000 | 10,000,000 |
Reliability is given as a fraction of 255. That is, 255 is 100 percent reliability or a perfectly stable link.
Load is given as a fraction of 255. A load of 255 indicates a completely saturated link.
The following example sets the metric weights to slightly different values than the defaults:
router igrp 109
network 131.108.0.0
metric weights 0 2 0 2 0 0
A dagger () indicates that the command is documented in another chapter.
bandwidth
delay
metric holddown
metric maximum-hops
Use this form of the neighbor router configuration command to define a neighboring router with which to exchange routing information. Use the no neighbor command to remove an entry.
neighbor ip-address
ip-address | IP address of a peer router with which routing information will be exchanged |
No neighboring routers are defined.
Router configuration
For exterior routing protocol EGP, this command specifies routing peers. For normally broadcast protocols such as IGRP or RIP, this command permits the point-to-point (nonbroadcast) exchange of routing information. When used in combination with the passive-interface router configuration command, routing information can be exchanged between a subset of routers on a LAN.
Multiple neighbor commands can be used to specify additional neighbors or peers.
OSPF has its own version of the neighbor command. See the neighbor (OSPF) command page in this chapter.
The following example establishes an EGP neighbor:
autonomous-system 109
router egp 110
neighbor 131.108.1.1
In the following example, IGRP updates are sent to all interfaces on network 131.108.0.0 except interface Ethernet 1. However, in this case a neighbor router configuration command is included. This command permits the sending of routing updates to specific neighbors. One copy of the routing update is generated per neighbor.
router igrp 109
network 131.108.0.0
passive-interface ethernet 1
neighbor 131.108.20.4
passive-interface
Use this form of the neighbor router configuration command to configure OSPF routers interconnecting to nonbroadcast networks. Use the no form of this command with the appropriate IP address and arguments to remove the configuration.
neighbor ip-address [priority number] [poll-interval seconds]
ip-address | Interface IP address of the neighbor. |
priority number | (Optional) 8-bit number indicating the router priority value of the nonbroadcast neighbor associated with the IP address specified. The default is 0. |
poll-interval seconds | (Optional) Unsigned integer value reflecting the poll interval. RFC 1247 recommends that this value should be much larger than the Hello interval. The default is 2 minutes (120 seconds). |
No configuration is specified.
Router configuration
X.25 and Frame Relay provide an optional broadcast capability that can be configured in the map to allow OSPF to run as a broadcast network. At the OSPF level you can configure the router as a broadcast network. See the x25 map and frame-relay map interface configuration command descriptions in "X.25 Commands" and "Frame Relay Commands" chapters, respectively, of this manual for more detail.
One neighbor entry must be included in the router's configuration for each known nonbroadcast network neighbor. The neighbor address has to be on the primary address of the interface.
If a neighboring router has become inactive (Hello packets have not been seen for the Router DeadInterval period), it may still be necessary to send Hello packets to the dead neighbor. These Hello packets will be sent at a reduced rate called Poll Interval.
When the router first starts up, it sends only Hello packets to those routers with non-zero priority, that is, routers which are eligible to become designated routers (DR) and backup designated routers (BDR). After DR and BDR are selected, DR and BDR will then start sending Hello packets to all neighbors in order to form adjacencies.
The following example declares a router at address 131.108.3.4 on a nonbroadcast network, with a priority of 1 and a poll-interval of 180:
router ospf
neighbor 131.108.3.4 priority 1 poll-interval 180
ip ospf priority
Use the neighbor advertisement-interval router configuration command to set the minimum interval between sending BGP routing updates. Use the no neighbor advertisement-interval command to remove an entry.
neighbor {address | tag} advertisement-interval seconds
address | Neighbor address. |
tag | Neighbor tag. |
seconds | Time in seconds. Integer from 0 through 600. |
30 seconds for external peers and 5 seconds for internal peers.
Router configuration
In the following example, the minimum time between sending BGP routing updates is set to
10 seconds:
router bgp 5
neighbor 4.4.4.4 advertisement-interval 10
Use the neighbor any router configuration command to control how neighbor entries are added to the routing table for both EGP and BGP. The no neighbor any command removes the configuration.
neighbor any [access-list-number]
access-list-number | (Optional) Access list number the neighbor must be accepted by to be allowed to peer with the EGP or BGP process. If no list is specified, any neighbor will be allowed to peer with the router. |
No configuration is specified.
Router configuration
The following example configuration illustrates the use of the neighbor any command in conjunction with the access-list global configuration command:
access-list 1 permit 10.0.0.0 0.255.255.255
! global access list assignment
router egp 0
neighbor any 1
A dagger () indicates that the command is documented in another chapter.
access-list
neighbor any third-party
router egp 0
Use the neighbor any third-party router configuration command to configure an EGP process that determine which neighbors will be treated as the next hop in EGP advertisements. The no neighbor any third-party command removes the configuration.
neighbor any third-party ip-address [internal | external]
ip-address | IP address of the third-party router that is to be the next hop in EGP advertisements. |
internal | (Optional) Indicates that the third-party router should be listed in the internal section of the EGP update. |
external | (Optional) Indicates that the third-party router should be listed in the external section of the EGP update. |
No EGP process is configured.
Router configuration
The following example illustrates how to specify the particular neighbors that an EGP process will view as peers:
access-list 2 permit 10.0.0.0 0.255.255.255
! global access list assignment
router egp 0
neighbor any 2
neighbor any third-party 10.1.1.1
neighbor any
router egp 0
Use the neighbor configure-neighbors router configuration command to instruct the router to treat temporary neighbors that have been accepted by a template as if they had been configured by hand. The no form of this command causes any new neighbor accepted by the template to be treated as temporary.
neighbor template-name configure-neighbors
template-name | A user selectable designation that identifies a particular template (an arbitrary word). |
New neighbors are treated as temporary.
Router configuration
Under normal circumstances, neighbors that are allowed to connect to the router because you had configured a template are treated as temporary. When a temporary neighbor disconnects, the local router will not try to actively reestablish a connection with it. In addition, information about temporary neighbors will not show up in the router configuration (write terminal).
When configure-neighbors is enabled on a particular template, any neighbor accepted by that template will be treated as if it had been manually configured. These neighbors will show up in write terminal displays and will be written to the nonvolatile configuration if a write memory command is issued.
In the following example, any BGP speaker matching access-list 7 can connect to the router and exchange information. Any neighbor that connects will be treated as if it had been manually configured.
access-list 7 permit 168.89.3.0 0.0.0.255
neighbor internal-ethernet neighbor-list 7
neighbor internal-ethernet configure-neighbors
neighbor neighbor-list
Use the neighbor distribute-list router configuration command to distribute BGP neighbor information as specified in an access list. Use the no form of this command to remove an entry.
neighbor ip-address distribute-list access-list-number {in | out}
ip-address | Neighbor's IP address. |
access-list-number | Predefined access list number. Only standard access lists can be used with this command. |
in | Access list is applied to incoming advertisements to that neighbor. |
out | Access list is applied to outgoing advertisements from that neighbor. |
No BGP neighbor is specified.
Router configuration
Using distribute lists is one of two ways to filter BGP advertisements. The other way is to use AS-path filters, as with the ip as-path access-list global configuration command and the neighbor
filter-list command.
The following example applies list 39 to incoming advertisements to neighbor 120.23.4.1:
router bgp 109
network 131.108.0.0
neighbor 120.23.4.1 distribute-list 39 in
ip as-path access-list
neighbor filter-list
Use the neighbor ebgp-multihop router configuration command to accept and attempt BGP connections to external peers residing on networks that are not directly connected. Use the no form of this command to return to the default of allowing only directly connected neighbors.
neighbor ip-address ebgp-multihop
ip-address | IP address of the BGP-speaking neighbor. |
Only directly connected neighbors are allowed.
Router configuration
This feature should only be used under the guidance of technical support staff.
The following example allows connections to or from neighbor 131.108.1.1, which resides on a network that is not directly connected.
router bgp 109
neighbor 131.108.1.1 ebgp-multihop
Use the neighbor filter-list router configuration command to set up BGP filters, using access lists defined with the ip as-path access-list command. Use the no form of this command to disable this function.
neighbor ip-address filter-list access-list-number {in | out | weight weight}
ip-address | IP address of the neighbor. |
access-list-number | Predefined autonomous system path access list number. |
in | Access list to incoming routes. |
out | Access list to outgoing routes. |
weight weight | Assigns a relative importance to incoming routes matching autonomous system paths. Acceptable values are 0 to 65535. |
Disabled
Router configuration
This command establishes filters on both inbound and outbound BGP routes. Any number of weight filters are allowed on a per-neighbor basis, but only one in or out filter is allowed. The weight of a route affects BGP's route-selection rules.
The implemented weight is based on the first matched autonomous system path. Weights indicated when an autonomous system path is matched override the weights assigned by global neighbor commands. In other words, the weights assigned with the match as-path and set weight route-map commands override the weights assigned using the neighbor weight and neighbor filter-list commands.
See the "Regular Expressions" appendix for information on forming regular expressions.
In the following example, the BGP neighbor with IP address 128.125.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 123:
ip as-path access-list 1 deny _123_
ip as-path access-list 1 deny ^123 .*
! The space in the above expression (^123 .*)is required.
router bgp 109
network 131.108.0.0
neighbor 129.140.6.6 remote-as 123
neighbor 128.125.1.1 remote-as 47
neighbor 128.125.1.1 filter-list 1 out
ip as-path access-list
neighbor distribute-list
neighbor weight
Use the neighbor neighbor-list router configuration command to configure BGP to support anonymous neighbor peers by configuring a neighbor template. Use the no form of this command to delete the template, and also cause any temporary neighbors accepted by the template to be shut down and removed.
neighbor template-name neighbor-list access-list-number
template-name | A user selectable designation that identifies a particular template (an arbitrary word). |
access-list-number | An IP access list number in the range 1 through 99. |
No configuration is defined.
Router configuration
To specify a group of anonymous neighbors, configure a neighbor template rather than specifically configure each neighbor. The template allows you to specify an IP access list which defines remote systems that can establish a BGP connection to the router. External BGP peers must be on a directly connected Ethernet unless they are overridden by the neighbor ebgp-multihop command.
Once you specify a template, you configure the template as if it were a regular neighbor entry, such as setting the protocol version or filter lists, so that anonymous neighbors accepted by the template will receive the settings of the template.
These neighbors accepted by the template appear in the show ip bgp summary and show ip bgp neighbor displays, although they do not appear in the router configuration. When the session is disconnected, all knowledge about the neighbor is discarded and the router will not attempt to actively re-establish a connection.
You can use the neighbor configure-neighbors command to request that the router treat peers learned through a template as if they were manually configured neighbors. These peers will then show up in write terminal displays and can be stored as part of the nonvolatile configuration.
In the following example, any BGP speaker from 168.89.3.0 can connect to the router and exchange information:
access-list 7 permit 168.89.3.0 0.0.0.255
neighbor internal-ethernet neighbor-list 7
neighbor internal-ethernet configure-neighbors
In the following example, any BGP speaker in the connected internet can establish a BGP connection to the local router, and the local router will send them routing information. However, the distribute-list clause instructs the local router to ignore all information these remote BGP speakers send to it.
access-list 9 permit 0.0.0.0 255.255.255.255
access-list 10 deny 0.0.0.0 255.255.255.255
neighbor route-server-peers neighbor-list 9
neighbor route-server-peers distribute-list 10 in
access-list (standard)
neighbor configure-neighbors
neighbor ebgp-multihop
Use the neighbor next-hop-self router configuration command to configure the router to disable next-hop processing on BGP updates. Use the no neighbor next-hop-self command to disable this feature.
neighbor ip-address next-hop-self
ip-address | IP address of the BGP-speaking neighbor |
Disabled
Router configuration
This command is useful in nonmeshed networks such as Frame Relay or X.25 where BGP neighbors may not have direct access to all other neighbors on the same IP subnet.
The following example forces all updates destined for 131.108.1.1 to advertise this router as the next hop:
router bgp 109
neighbor 131.108.1.1 next-hop-self
Use the neighbor remote-as router configuration command to add an entry to the BGP neighbor table. Use the no form of this command to remove a neighbor.
neighbor ip-address remote-as number
ip-address | Neighbor's IP address |
number | Autonomous system to which the neighbor belongs |
There are no BGP neighbor peers.
Router configuration
Specifying a neighbor with an autonomous system number that matches the autonomous system number specified in the router bgp global configuration command identifies the neighbor as internal to the local autonomous system. Otherwise, the neighbor is considered external.
The following example specifies that the router at the address 131.108.1.2 is a neighbor in autonomous system number 109:
router bgp 110
network 131.108.0.0
neighbor 131.108.1.2 remote-as 109
In the following example, a BGP router is assigned to autonomous system 109, and two networks are listed as originating in the autonomous system. Then the addresses of three remote routers (and their autonomous systems) are listed. The router being configured will share information about networks 131.108.0.0 and 192.31.7.0 with the neighbor routers. The first router listed is in the same Class B network address space, but in a different autonomous system; the second neighbor command illustrates specification of an internal neighbor (with the same autonomous system number) at address 131.108.234.2; and the last neighbor command specifies a neighbor on a different network.
router bgp 109
network 131.108.0.0
network 192.31.7.0
neighbor 131.108.200.1 remote-as 167
neighbor 131.108.234.2 remote-as 109
neighbor 150.136.64.19 remote-as 99
address | Neighbor's IP address |
tag | Neighbor tag |
route-map-name | Name of route map |
in | Apply to incoming routes |
out | Apply to outgoing routes |
No route maps are applied to a peer.
Router configuration
If an outbound route map is specified, it is proper behavior to only advertise routes that match at least one section of the route map.
In the following example, route map "internal-map" is applied to incoming route from 198.92.70.24:
router bgp 5
neighbor 198.92.70.24 route-map internal-map in
!
route-map internal-map
match as-path 1
set local-preference 100
Use the neighbor third-party router configuration command to send updates regarding EGP third-party routers. Use the no form of this command to disable these updates.
neighbor ip-address third-party third-party-ip-address [internal | external]
ip-address | IP address of the EGP peer. |
third-party-ip-address | Address of the third-party router on the network shared by the Cisco router and the EGP peer specified by address. |
internal | (Optional) Indicates that the third-party router should be listed in the internal section of the EGP update. This is the default. |
external | (Optional) Indicates that the third-party router should be listed in the external section of the EGP update. |
Disabled
Router configuration
Using this third-party mechanism, EGP tells its peer that another router (the third party) on the shared network is the appropriate router for some set of destinations. If updates mentioning third-party routers are desired, use this command.
All networks reachable through the third-party router will be listed in the EGP updates as reachable by the router. The optional internal and external keywords indicate whether the third-party router should be listed in the internal or external section of the EGP update. Normally, all networks are mentioned in the internal section.
This command can be used multiple times to specify additional third-party routers.
In the following example, routes learned from router 131.108.6.99 will be advertised to 131.108.6.5 as third-party internal routes:
neighbor 131.108.6.5 third-party 131.108.6.99 internal
In the following example, routes learned from 131.108.6.100 will be advertised to 131.108.6.5 as third-party external routes:
neighbor 131.108.6.5 third-party 131.108.6.100 external
Use the neighbor update-source router configuration command to configure the router to allow internal BGP sessions to use any operational interface for TCP connections. The no form of this command restores the interface assignment to the closest interface, also called the
best-local-address.
ip-address | IP address of the BGP-speaking neighbor |
interface | Loopback interface |
Best-local-address
Router configuration
This feature works in conjunction with the Loopback interface feature described in the "Configuring Interfaces" chapter of the Router Products Configuration Guide.
In the following example, BGP TCP connections for the specified neighbor will be sourced with Loopback interface's IP address rather than the best-local-address:
router bgp 110
network 160.89.0.0
neighbor 160.89.2.3 remote-as 110
neighbor 160.89.2.3 update-source Loopback0
Use the neighbor version router configuration command to configure the router to accept only a particular version. The no form of this command returns the version to the default level of that neighbor.
neighbor ip-address version value
ip-address | IP address of the BGP-speaking neighbor. |
version value | Version number. The version can be set to 2 to force the router to only use Version 2 with the specified neighbor. The default is to use Version 4 of BGP and dynamically negotiate down to Version 2 if requested. |
Version 4
Router configuration
Entering this command disables dynamic version negotiation.
Our implementation of BGP supports Versions 2, 3, and 4 of BGP. If the neighbor does not accept default version 4, dynamic version negotiation is implemented to negotiate down to version 2.
The following example locks down to Version 4 of the BGP protocol:
router bgp 109
neighbor 131.104.27.2 version 4
Use the neighbor weight router configuration command to specify a weight to assign to a specific neighbor connection. The no form of this command removes the assignment.
neighbor ip-address weight weight
ip-address | Neighbor's IP address. |
weight weight | Weight to assign. Acceptable values are 0 to 65535. |
Routes learned through another BGP peer have a default weight of 0 and routes sourced by the local router have a default weight of 32768.
Router configuration
All routes learned from this neighbor will have the assigned weight initially. The route with the highest weight will be chosen as the preferred route when multiple routes are available to a particular network.
The weights assigned with the match as-path and set weight route-map commands override the weights assigned using the neighbor weight and neighbor filter-list commands.
The following example sets the weight of all routes learned via 151.23.12.1 to 50:
router bgp 109
neighbor 151.23.12.1 weight 50
neighbor distribute-list
neighbor filter-list
Use the net router configuration command to configure a Network Entity Title (NET) for the routing process. The no net command removes a specific NET; you must specify the NET.
net network-entity-title
network-entity-title | NET that specifies the area address and the system ID for an IS-IS routing process. This argument can be either an address or a name. |
No NET is configured.
Router configuration
For IS-IS, multiple NETs per router are allowed, with a maximum of three. There is no default value for this command.
The following example specifies a single NET:
router isis Pieinthesky
net 47.0004.004d.0001.0000.0c11.1111.00
Use this form of the network router configuration command to specify the list of networks for the BGP routing process. Use the no form of this command to remove the entry.
network network-number mask network-mask
network-number | IP address of a peer router with which routing information will be exchanged |
network-mask | Network mask address |
No networks are specified.
Router configuration
These types of networks can be learned from connected routes, dynamic routing, and from static route sources.
A maximum of 200 network commands may be specified for a single BGP process.
The following example sets up network 131.108.0.0 to be included in the router's BGP updates:
router bgp 120
network 131.108.0.0
router bgp
network backdoor
network mask
network weight
Use this form of the network router configuration command to specify the list of networks for the EGP routing process. The no form of this command removes a network from the list.
network network-number
network-number | IP address of a peer router with which routing information will be exchanged |
No networks are specified.
Router configuration
The networks to be advertised to the EGP peers of an EGP routing process are advertised with a distance of zero. The restrictions on the network you specify are that it must appear in the routing table, and the network number must not contain any subnet information. The network can be connected, statically configured, or redistributed into EGP from other routing protocols. Multiple commands can be used to specify additional networks.
The following example illustrates a typical configuration for an EGP router process. The router is in autonomous system 109 and is peering with routers in autonomous system 164. It will advertise the networks 131.108.0.0 and 192.31.7.0 to the router in autonomous system 164, 10.2.0.2. The information sent and received from peer routers can be filtered in various ways, including blocking information from certain routers and suppressing the advertisement of specific routes.
autonomous-system 109
router egp 164
network 131.108.0.0
network 192.31.7.0
neighbor 10.2.0.2
router egp
Use this form of the network router configuration command to specify a list of networks for the IGRP routing process. The no form of this command removes a network from the list.
network network-number
network-number | IP address of the directly connected networks |
No networks are specified.
Router configuration
The network number specified must not contain any subnet information. You can specify multiple network commands.
IGRP sends updates to the interfaces in the specified network(s). Also, if an interface's network is not specified, it will not be advertised in any IGRP update.
The following example configures a router for IGRP and assigns autonomous system 109. The network commands indicate the networks directly connected to the router.
router igrp 109
network 131.108.0.0
network 192.31.7.0
router igrp
Use this form of the network router configuration command to specify a list of networks for the RIP routing process. The no network command removes a network from the list.
network network-number
network-number | IP address of the network of directly connected networks. |
No networks are specified.
Router configuration
The network number specified must not contain any subnet information. You can specify multiple network commands. RIP routing updates will be sent and received only through interfaces on this network.
RIP sends updates to the interfaces in the specified network(s). Also, if an interface's network is not specified, it will not be advertised in any RIP update.
The following example defines RIP as the routing protocol to be used on all interfaces connected to networks 128.99.0.0 and 192.31.7.0:
router rip
network 128.99.0.0
network 192.31.7.0
router rip
Use the network area router configuration command to define the interfaces on which OSPF runs and to define the area ID for those interfaces. The no form of this command disables OSPF routing for interfaces defined with the address wildcard-mask pair; you must specify the complete address range and area ID.
network address wildcard-mask area area-id
address | IP address. |
wildcard-mask | IP-address-type mask that includes "don't care" bits. |
area-id | Area that is to be associated with the OSPF address range. It can be specified as either a decimal value or as an IP address. If you intend to associate areas with IP subnets, you can specify a subnet address as the area-id. |
Disabled
Router configuration
The address and wildcard-mask arguments together allow you to define one or multiple interfaces to be associated with a specific OSPF area using a single command. Using the wildcard-mask allows you to define one or multiple interfaces to be associated with a specific OSPF area using a single command. If you intend to associate areas with IP subnets, you can specify a subnet address as the area-id.
The router sequentially evaluates the address/wildcard-mask pair for each interface as follows:
1. The wildcard-mask is logically ORed with the interface IP address.
2. The wildcard-mask is logically ORed with address in the network command.
3. The router compares the two resulting values.
4. If they match, OSPF is enabled on the associated interface and this interface is attached to the OSPF area specified.
In the following partial example, OSPF routing process 109 is initialized, and four OSPF areas are defined: 10.9.50.0, 2, 3, and 0. Areas 10.9.50.0, 2, and 3 mask specific address ranges, while Area 0 enables OSPF for all other networks.
router ospf 109
network 131.108.20.0 0.0.0.255 area 10.9.50.0
network 131.108.0.0 0.0.255.255 area 2
network 131.109.10.0 0.0.0.255 area 3
network 0.0.0.0 255.255.255.255 area 0
router ospf
Use the network backdoor router configuration command to specify a backdoor route to a BGP border router that will provide better information about the network. The no form of this command removes an address from the list.
network address backdoor
address | IP address of the network to which you want a backdoor route |
No network is advertised.
Router configuration
A backdoor network is treated as a local network, except that it is not advertised.
The following example configures network 131.108.0.0 as a local network and network 192.31.7.0 as a backdoor network:
router bgp 109
network 131.108.0.0
network 192.31.7.0 backdoor
Use the network weight command to assigns an absolute weight, or importance, to a BGP network. Use the no form of the command to delete the entry.
network address weight weight
address | IP address of the network. |
weight weight | Absolute weight. Integer from 0 to 65535. |
Weight is unmodified. Weight is zero if the original default weight has not been modified by other router configuration commands.
Router configuration
The weight specified by this command overrides a weight assigned by the redistribute command.
In the following example,
router bgp 5
network 193.0.0.0 weight 100
Use the offset-list router configuration command to add or remove a positive offset to incoming and outgoing metrics for networks matching a specified access list (for IGRP and RIP only). The no offset-list command with the appropriate keywords removes the offset list.
offset-list {in | out} offset [access-list-number]
in | Applies the access list to incoming metrics. |
out | Applies the access list to outgoing metrics. |
offset | Positive offset to be applied to metrics for networks matching the access list. If the offset is zero, no action is taken. |
access-list-number | (Optional) Access list to be applied. If unspecified, the argument supplied to offset is applied to all metrics. If offset is zero, no action is taken. For IGRP, the offset is added to the delay component only. Must be a standard access list. |
Disabled
Router configuration
The following example for a router using IGRP applies an offset of 10 to its delay component for all outgoing metrics:
offset-list out 10
interface | Specified interface. The particular subnet will continue to be advertised to other interfaces. Updates from other routers on that interface continue to be received and processed. |
Routing updates are sent on the interface.
Router configuration
For OSPF, OSPF routing information is neither sent nor received through the specified router interface. The specified interface address appears as a stub network in the OSPF domain.
For IS-IS, this command instructs IS-IS to advertise the IP addresses for the specified interface without actually running IS-IS on that interface. The no form of this command for IS-IS disables advertising IP addresses for the specified address.
The following example sends IGRP updates to all interfaces on network 131.108.0.0 except interface Ethernet 1:
router igrp 109
network 131.108.0.0
passive-interface ethernet 1
The following configuration enables IS-IS on interfaces Ethernet 1 and serial 0 and advertises the IP addresses of Ethernet 0 in its Link State PDUs:
router isis Finance
passive-interface Ethernet 0
interface Ethernet 1
ip router isis Finance
interface serial 0
ip router isis Finance
protocol | The source protocol from which routes are being redistributed. It can be one of the following keywords: bgp, egp, igrp, isis, ospf, static [ip], connected and rip. The keyword static [ip] is used to redistribute IP static routes. The optional ip keyword is used when redistributing into IS-IS. The keyword connected refers to routes which are established automatically by virtue of having enabled IP on an interface. For routing protocols such as OSPF and IS-IS, these routes will be redistributed as external to the autonomous system. |
process-id | For bgp, egp, or igrp, this is an autonomous system number, a 16-bit decimal number. |
level-1 | For IS-IS, Level 1 routes are redistributed into other IP routing protocols independently. |
level-1-2 | For IS-IS, both Level 1 and Level 2 routes are redistributed into other IP routing protocols. |
level-2 | For IS-IS, Level 2 routes are redistributed into other IP routing protocols independently. |
metric metric-value | (Optional) Metric used for the redistributed route. If a value is not specified for this option, and no value is specified using the default-metric router configuration command, the default metric value is 0. Use a value consistent with the destination protocol. |
metric-type type-value | (Optional) For OSPF, the external link type associated with the default route advertised into the OSPF routing domain. It can be one of two values: 1---Type 1 external route 2---Type 2 external route If a metric-type is not specified, the router adopts a Type 2 external route. For IS-IS, it can be one of two values: internal---IS-IS metric which is < 63. external---IS-IS metric which is > 64 < 128. The default is internal. |
match {internal | external 1 | (Optional) For OSPF, the criteria by which OSPF routes are redistributed into other routing domains. Can be one of the following: internal---Routes that are internal to a specific autonomous system. external 1---Routes that are external to the autonomous system, but are to be imported to OSPF as type 1 external route. |
tag tag-value | (Optional) 32-bit decimal value attached to each external route. This is not used by the OSPF protocol itself. It may be used to communicate information between autonomous system boundary routers. If none is specified, then the remote autonomous system number is used for routes from BGP and EGP; for other protocols, zero (0) is used. |
route-map | (Optional) Route map should be interrogated to filter the importation of routes from this source routing protocol to the current routing protocol. If not specified, all routes are redistributed. If this keyword is specified, but no route map tags are listed, no routes will be imported. |
map-tag | Identifier of a configured route map. |
weight weight | Network weight when redistributing into BGP. An integer between 0 and 65535. |
subnets | (Optional) For redistributing routes into OSPF, the scope of redistribution for the specified protocol. |
See "Syntax Description" for the various defaults.
Router configuration
Changing or disabling any keyword will not affect the state of other keywords.
A router receiving a link-state protocol (LSP) with an internal metric will consider the cost of the route from itself to the redistributing router plus the advertised cost to reach the destination. An external metric only considers the advertised metric to reach the destination.
Routes learned from IP routing protocols can be redistributed at level-1 into an attached area or at level-2. The keyword level-1-2 allows both in a single command.
Redistributed routing information should always be filtered by the distribute-list out router configuration command. This ensures that only those routes intended by the administrator are passed along to the receiving routing protocol.
Whenever you use the redistribute or the default-information router configuration commands to redistribute routes into an OSPF routing domain, the router automatically becomes an autonomous system boundary router. However, an autonomous system boundary router does not, by default, generate a default route into the OSPF routing domain.
When routes are redistributed between OSPF processes, no OSPF metrics are preserved.
The only connected routes affected by this redistribute command are the routes not specified by the network command.
You cannot use the default-metric command to affect the metric used to advertise connected routes.
Default redistribution of IGPs or EGP into BGP is not allowed unless default-information originate is specified.
When routes are redistributed into OSPF and no metric is specified in the metric keyword, the default metric that OSPF uses is 20 for routes from all protocols except BGP route, which gets a metric of 1.
The following are examples of the various configurations you would use to redistribute one routing protocol into another routing protocol.
The following example configuration causes OSPF routes to be redistributed into a BGP domain:
router bgp 109
redistribute ospf...
The following example configuration causes IGRP routes to be redistributed into an OSPF domain:
router ospf 110
redistribute igrp...
The following example illustrates the use of this form of the redistribute command, with the match keyword and its options enabled:
router igrp 108
redistribute ospf 109 match internal external 1 external 2
The following example causes the specified IGRP process routes to be redistributed into an OSPF domain. The IGRP-derived metric will be remapped to 100 and RIP routes to 200.
router ospf 109
redistribute igrp 108 metric 100 subnets
redistribute rip metric 200 subnets
In the following example, BGP routes are configured to be redistributed into IS-IS. The link-state cost is specified as 5, and the metric type will be set to external, indicating that it has lower priority than internal metrics.
router isis
redistribute bgp 120 metric 5 metric-type external
default-information originate
distribute-list out
route-map
show route-map
map-tag | Defines a meaningful name for the route map. The redistribute router configuration command uses this name to reference this route map. Multiple route maps may share the same map tag name. |
permit | (Optional) If the match criteria are met for this route map, and permit is specified, the route is redistributed as controlled by the set actions. If the match criteria are not met, and permit is specified, the next route map with the same map-tag is tested. If a route passes none of the match criteria for the set of route maps sharing the same name, it is not redistributed by that set. |
deny | (Optional) If the match criteria are met for the route map, and deny is specified, the route is not redistributed, and no further route maps sharing the same map tag name will be examined. |
sequence-number | (Optional) Number that indicates the position a new route map is to have in the list of route maps already configured with the same name. If given with the no form of this command, it specifies the position of the route map that should be deleted. |
No default available.
Global configuration
Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria---the conditions under which redistribution is allowed for the current route-map. The set commands specify the set actions---the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
Use route maps when you wish to have detailed control over how routes are redistributed between routing processes. The destination routing protocol is the one you specify with the router global configuration command. The source routing protocol is the one you specify with the redistribute router configuration command. See the following example as an illustration of how route maps are configured.
The following example redistributes all OSPF routes into IGRP:
router igrp 109
redistribute ospf 110
default metric 1000 100 255 1 1500
The following example redistributes RIP routes with a hop count equal to 1 into OSPF. These routes will be redistributed into OSPF as external link state advertisements with a metric of 5, metric type of Type 1 and a tag equal to 1.
router ospf 109
redistribute rip route-map rip-to-ospf
route-map rip-to-ospf permit
match metric 1
set metric 5
set metric-type type1
set tag 1
match
redistribute
set
show route-map
Use the router bgp global configuration command to configure the Border Gateway Protocol (BGP) routing process. Use the no router bgp command to remove the routing process.
router bgp autonomous-system
autonomous-system | Identifies the router to other BGP routers and tags the routing information passed along. |
No BGP routing process is enabled by default.
Global configuration
This command allows you to set up a distributed routing core that automatically guarantees the loop-free exchange of routing information between autonomous systems.
The following example configures a BGP process for autonomous system 120:
router bgp 120
neighbor
network (BGP)
timers bgp
remote-as | Identifies the autonomous system number the router expects its peers to be advertising in their EGP messages. |
No EGP routing process is defined.
Global configuration
You must specify the autonomous system number before starting EGP. The local autonomous system number will be included in EGP messages sent by the router. The software does not insist that the actual remote autonomous system number match the configured autonomous system numbers. The output from the debug ip-egp EXEC command will advise of any discrepancies.
The following example assigns a router to autonomous system 109 and is peering with routers in autonomous system 164:
autonomous-system 109
router egp 164
autonomous-system
neighbor
network (EGP)
timers egp
This command has no arguments or keywords.
Disabled
Global configuration
Core gateways are central clearinghouses of routing information. Only one core gateway process can be configured in a router.
The router egp 0 global configuration command allows a specific router to have an EGP process that will enable it to act as a peer with any reachable autonomous system and information is exchanged freely between autonomous systems.
Normally, an EGP process expects to communicate with neighbors from a single autonomous system. Because all neighbors are in the same autonomous system, the EGP process assumes that these neighbors all have consistent internal information. Therefore, if the EGP process is informed about a route from one of its neighbors, it will not send it out to other neighbors.
With core EGP, the assumption is that all neighbors are from different autonomous systems, and all have inconsistent information. In this case, the EGP process distributes routes from one neighbor to all others (but not back to the originator). This allows the EGP process to be a central clearinghouse for information.
The following example illustrates how an EGP core gateway can be configured:
access-list 1 permit 10.0.0.0 0.255.255.255
! global access list assignment
router egp 0
neighbor any 1
network 131.108.0.0
neighbor any
neighbor any third-party
Use the router igrp global configuration command to configure the Interior Gateway Routing Protocol (IGRP) routing process. Use the no router igrp command to shut down the routing process on the specified autonomous system.
router igrp autonomous-system
autonomous-system | Identifies the routes to the other IGRP routers and is used to tag the routing information. |
No IGRP routing process is defined.
Global configuration
The following example shows how to configure an IGRP routing process and assign autonomous system 109:
router igrp 109
network (IGRP)
tag | (Optional) Defines a meaningful name for a routing process. If it is not specified, a null tag is assumed and the process is referenced with a null tag. This name must be unique among all IP router processes for a given router. |
Disabled
Global configuration
You can specify only one IS-IS process per router. Only one IS-IS process is allowed whether you run it in integrated mode, ISO CLNS only, or IP only.
The following example configures the router for IP routing and enables the IS-IS routing protocol:
ip routing
router isis
ip router isis
net
process-id | Internally used identification parameter for an OSPF routing process. It is locally assigned and can be any positive integer. A unique value is assigned for each OSPF routing process. |
No OSPF routing process is defined.
Global configuration
You can specify multiple OSPF routing processes in each router.
The following example shows how to configure an OSPF routing process and assign a process ID of 109:
router ospf 109
network (OSPF)
Use the router rip global configuration command to configure the Routing Information Protocol (RIP) routing process. Turn off the RIP routing process using the no router rip command.
router ripThis command has no arguments or keywords.
No RIP routing process is defined.
Global configuration
The following example shows how to begin the RIP routing process:
router rip
network (RIP)
Use the set automatic-tag route-map configuration command to automatically compute the tag value. Use the no set automatic-tag command to disable this function.
set automatic-tagThis command has no arguments or keywords.
Disabled
Route-map configuration
You must have a match clause (even if it points to a "permit everything" list) if you want to set tags.
The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map's match criteria are met. When all match criteria are met, all set actions are performed.
In the following example, the router is configured to automatically compute the tag value for the BGP learned routes.
route-map tag
match as path 10
set automatic-tag
!
router bgp 100
table-map tag
match
route-map
Use the set level route-map configuration command to indicate where to import routes. Use the no form of this command to delete the entry.
set level {level-1 | level-2 | level-1-2 | stub-area | backbone}
level-1 | Import into a Level-1 area |
level-2 | Import into Level-2 sub-domain |
level-1-2 | Import into Level-1 and Level-2 |
stub-area | Import into OSPF NSSA area |
backbone | Import into OSPF backbone area |
Disabled
For IS-IS destinations, the default value is level-2. For OSPF destinations, the default value is backbone.
Route-map configuration
The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map's match criteria are met. When all match criteria are met, all set actions are performed.
In the following example, routes will be imported into the Level 1 area:
route-map name
set level level-l
route-map
match
value | Preference value. An integer from 0 through 4294967295. |
Preference value of 100
Route-map configuration
The preference is sent only to all routers in the local autonomous system.
You must have a match clause (even if it points to a "permit everything" list) if you want to set tags.
The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map's match criteria are met. When all match criteria are met, all set actions are performed.
You can change the default preference value with the bgp default local-preference command.
In the following example, the local preference of is set to 100 for all routes that are included in access list 1:
route-map map-preference
match as-path 1
set local-preference 100
match
route-map
Use the set metric route-map configuration command to set the metric value for the destination routing protocol. Use the no form of this command to return to the default metric value.
set metric metric-value
metric-value | Metric value or IGRP bandwidth in kilobits per second. An integer from 0 through 294967295. |
Default metric value.
Route-map configuration
The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map's match criteria are met. When all match criteria are met, all set actions are performed.
In the following example, the metric value for the destination routing protocol is set to 100:
route-map set-metric
set metric 100
match
route-map
Use the set metric-type route-map command to set the metric type for the destination routing protocol:
set metric-type {internal | external | type-1 | type-2}
internal | IS-IS internal metric |
external | IS-IS external metric |
type-1 | OSPF external type 1 metric |
type-2 | OSPF external type 2 metric |
Disabled
Route-map configuration
The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map's match criteria are met. When all match criteria are met, all set actions are performed.
In the following example, the metric type of the destination protocol is set to OSPF external type 1:
route-map map-type
set metric-type type-1
match
route-map
Use the set next-hop route-map configuration command to specify the address of the next hop. Use the no form of this command to delete the entry.
set next-hop next-hop
next-hop | IP address of the next hop router |
Default next-hop address.
Route-map configuration
You must have a match clause (even if it points to a "permit everything" list) if you want to set tags.
The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map's match criteria are met. When all match criteria are met, all set actions are performed.
In the following example, routes that pass the access list have the next hop set to 198.92.70.24:
route-map map_hop
match address 5
set next-hop 198.92.70.24
match
route-map
Use the set origin route-map configuration command to set the BGP origin code. Use the no form of this command to delete the entry.
set origin {igp | egp as | incomplete}
igp | Remote EGP |
egp | Local IGP |
as | Remote autonomous system. An integer from 0 through 65535. |
incomplete | Unknown heritage |
Default origin, based on route in main IP routing table.
Route-map configuration
You must have a match clause (even if it points to a "permit everything" list) if you want to set tags.
The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map's match criteria are met. When all match criteria are met, all set actions are performed.
In the following example, routes that pass the route map have the origin set to IGP:
route-map set_origin
match as-path 10
set origin igp
match
route-map
Use the set tag route-map configuration command to set a tag value of the destination routing protocol. Use the no form of this command to delete the entry.
set tag tag-value
tag-value | Name for the tag. Integer from 0 through 4294967295. |
If not specified, the default action is to forward the tag in the source routing protocol onto the new destination protocol.
Route-map configuration
The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map's match criteria are met. When all match criteria are met, all set actions are performed.
In the following example, the tag value of the destination routing protocol is set to 5:
route-map tag
set tag 5
match
route-map
Use the set weight route-map configuration command to specify the BGP weight for the routing table. Use the no form of this command to delete the entry.
set weight weight
weight | Weight value. From 0 through 65535. |
The weight will not be changed by the specified route map.
Route-map configuration
You must have a match clause (even if it points to a "permit everything" list) if you want to set tags.
The implemented weight is based on the first matched autonomous system path. Weights indicated when an autonomous system path is matched override the weights assigned by global neighbor commands. In other words, the weights assigned with the match as-path and set weight route-map commands override the weights assigned using the neighbor weight and neighbor filter-list commands.
In the following example, the BGP weight for the routes matching the AS path access list is set to 200:
route-map set-weight
match as-path 10
set weight 200
match
route-map
Use the show ip bgp EXEC command to display a particular network in the BGP routing table.
show ip bgp [network] [network-mask] [subnets]
network | (Optional) Network number, entered to display a particular network in the BGP routing table. |
network-mask | (Optional) Displays all BGP routes matching the address/mask pair. |
subnets | (Optional) Displays route and more specific routes. |
EXEC
The following is sample output from the show ip bgp command:
Router# show ip bgp
BGP table version is 716977, local router ID is 193.0.32.1
Status codes: s suppressed, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* i3.0.0.0 193.0.22.1 0 100 0 1800 1239 ?
*>i 193.0.16.1 0 100 0 1800 1239 ?
* i6.0.0.0 193.0.22.1 0 100 0 1800 690 568 ?
*>i 193.0.16.1 0 100 0 1800 690 568 ?
* i7.0.0.0 193.0.22.1 0 100 0 1800 701 35 ?
*>i 193.0.16.1 0 100 0 1800 701 35 ?
* 198.92.72.24 0 1878 704 701 35 ?
* i8.0.0.0 193.0.22.1 0 100 0 1800 690 560 ?
*>i 193.0.16.1 0 100 0 1800 690 560 ?
* 198.92.72.24 0 1878 704 701 560 ?
* i13.0.0.0 193.0.22.1 0 100 0 1800 690 200 ?
*>i 193.0.16.1 0 100 0 1800 690 200 ?
* 198.92.72.24 0 1878 704 701 200 ?
* i15.0.0.0 193.0.22.1 0 100 0 1800 174 ?
*>i 193.0.16.1 0 100 0 1800 174 ?
* i16.0.0.0 193.0.22.1 0 100 0 1800 701 i
*>i 193.0.16.1 0 100 0 1800 701 i
* 198.92.72.24 0 1878 704 701 i
Table 17-3 describes significant fields shown in the display.
| Field | Description |
|---|---|
BGP table version is 716977 | Internal version number for the table. This is incremented any time the table changes. |
local router ID | An Internet address of the router. |
Status codes | Asterisk (*) indicates that the table entry is valid. |
Network | Internet address of the network the entry describes. |
Next Hop | IP address of the next system to use when forwarding a packet to the destination network. An entry of 0.0.0.0 indicates that the router has some non-BGP route to this network. |
Metric | If shown, is the value of the interautonomous system metric. This is frequently not used. |
Weight | Set through the use of autonomous system filters. |
Path | Autonomous system paths to the destination network. There can be one entry in this field for each autonomous system in the path. At the end of the path is the origin code for the path. |
LocPrf | Local preference value. Default is 100. |
The following is sample output from the show ip bgp subnets command:
Router# show ip bgp 198.92.0.0 255.255.0.0 subnets
BGP table version is 1738, local router ID is 198.92.72.24
Status codes: s suppressed, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 198.92.0.0 198.92.72.30 8896 32768 ?
* 198.92.72.30 0 109 108 ?
*> 198.92.1.0 198.92.72.30 8796 32768 ?
* 198.92.72.30 0 109 108 ?
*> 198.92.11.0 198.92.72.30 42482 32768 ?
* 198.92.72.30 0 109 108 ?
*> 198.92.14.0 198.92.72.30 8796 32768 ?
* 198.92.72.30 0 109 108 ?
*> 198.92.15.0 198.92.72.30 8696 32768 ?
* 198.92.72.30 0 109 108 ?
*> 198.92.16.0 198.92.72.30 1400 32768 ?
* 198.92.72.30 0 109 108 ?
*> 198.92.17.0 198.92.72.30 1400 32768 ?
* 198.92.72.30 0 109 108 ?
*> 198.92.18.0 198.92.72.30 8876 32768 ?
* 198.92.72.30 0 109 108 ?
*> 198.92.19.0 198.92.72.30 8876 32768 ?
* 198.92.72.30 0 109 108 ?
Use the show ip bgp cidr-only privileged EXEC command to display only routes with non-natural network masks.
show ip bgp cidr-onlyThis command has no arguments or keywords.
Privileged EXEC
The following is sample output for the show ip bgp cidr-only command:
Router# show ip bgp cidr-only
BGP table version is 220, local router ID is 198.92.73.131
Status codes: s suppressed, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 192.0.0.0/8 198.92.72.24 0 1878 ?
*> 198.92.0.0/16 198.92.72.30 0 108 ?
Use the show ip bgp filter-list privileged EXEC command to display routes that conform to a specified filter list.
show ip bgp filter-list access-list-number
access-list-number | Regular expression access list number from 1 through 199 |
Privileged EXEC
The following is sample output from the show ip bgp filter-list command:
Router# show ip bgp filter-list 2
BGP table version is 1738, local router ID is 198.92.72.24
Status codes: s suppressed, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 198.92.0.0 198.92.72.30 0 109 108 ?
* 198.92.1.0 198.92.72.30 0 109 108 ?
* 198.92.11.0 198.92.72.30 0 109 108 ?
* 198.92.14.0 198.92.72.30 0 109 108 ?
* 198.92.15.0 198.92.72.30 0 109 108 ?
* 198.92.16.0 198.92.72.30 0 109 108 ?
* 198.92.17.0 198.92.72.30 0 109 108 ?
* 198.92.18.0 198.92.72.30 0 109 108 ?
* 198.92.19.0 198.92.72.30 0 109 108 ?
* 198.92.24.0 198.92.72.30 0 109 108 ?
* 198.92.29.0 198.92.72.30 0 109 108 ?
* 198.92.30.0 198.92.72.30 0 109 108 ?
* 198.92.33.0 198.92.72.30 0 109 108 ?
* 198.92.35.0 198.92.72.30 0 109 108 ?
* 198.92.36.0 198.92.72.30 0 109 108 ?
* 198.92.37.0 198.92.72.30 0 109 108 ?
* 198.92.38.0 198.92.72.30 0 109 108 ?
* 198.92.39.0 198.92.72.30 0 109 108 ?
address | (Optional) Address of the neighbor whose routes you have learned from |
routes | (Optional) Routes of specified neighbors |
paths | (Optional) Autonomous system path of specified neighbor |
EXEC
The following is sample output from the show ip bgp neighbors command:
Router# show ip bgp neighbors
BGP neighbor is 131.108.6.68, remote AS 10, external link
BGP version 3, remote router ID 131.108.6.68
BGP state = Established, table version = 22, up for 0:00:13
Last read 0:00:12, hold time is 180, keepalive interval is 60 seconds
Received 24 messages, 0 notifications
Sent 28 messages, 4 notifications
Connections established 1; dropped 0
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Local host: 131.108.6.69, 12288 Foreign host: 131.108.6.68, 179
Enqueued packets for retransmit: 0, input: 0, saved: 0
Event Timers (current time is 835828):
Timer: Retrans TimeWait AckHold SendWnd KeepAlive
Starts: 20 0 18 0 0
Wakeups: 1 0 2 0 0
Next: 0 0 0 0 0
iss: 60876 snduna: 62649 sndnxt: 62649 sndwnd: 1872
irs: 95187024 rcvnxt: 95188733 rcvwnd: 1969 delrcvwnd: 271
SRTT: 364 ms, RTTO: 1691 ms, RTV: 481 ms, KRTT: 0 ms
minRTT: 4 ms, maxRTT: 340 ms, ACK hold: 300 ms
Flags: higher precedence
Datagrams (max data segment is 1450 bytes):
Rcvd: 36 (out of order: 0), with data: 18, total data bytes: 1708
Sent: 40 (retransmit: 1), with data: 36, total data bytes: 1817
Table 17-4 describes significant fields shown in the display.
| Field | Description |
|---|---|
BGP neighbor | Lists the IP address of the BGP neighbor and its autonomous system number. If the neighbor is in the same autonomous system as the router, then the link between them is internal. Otherwise, it is considered external. |
BGP version | Specifies that the BGP version being used to communicate with the remote router is BGP version 3; the neighbor's router ID (an IP address) is also specified. |
BGP state | Indicates the internal state of this BGP connection. |
table version | Indicates that the neighbor has been updated with this version of the primary BGP routing table. |
up time | Indicates the amount of time that the underlying TCP connection has been in existence. |
Last read | Time that BGP last read a message from this neighbor. |
hold time | Maximum amount of time that can elapse between messages from the peer. |
keepalive interval | Time period between sending keepalive packets, which help ensure that the TCP connection is up. |
Received | Number of received messages indicates the number of total BGP messages received from this peer, including keepalives. The number of notifications is the number of error messages received from the peer. |
Sent | The number of sent messages indicates the total number of BGP messages that have been sent to this peer, including keepalives. The number of notifications is the number of error messages that we have sent to this peer. |
Connections established | The number of connections established is a count of the number of times that we have established a TCP connection and the two peers have agreed speak BGP with each other. The number of dropped connections is the number of times that a good connection has failed or been taken down. |
The remainder of the display describes the status of the underlying TCP connection.
The following is sample output from the show ip bgp neighbors paths command:
Router# show ip bgp neighbors 198.92.72.24 paths
Address Refcount Metric Path
0x3BAE7C 41 0 1878 ?
0x3BA714 3 0 1878 1755 i
0x3BA58C 1 0 1878 i
Use the show ip bgp paths EXEC command to display all the BGP paths in the database.
show ip bgp pathsThis command has no arguments or keywords.
EXEC
The following is sample output from the show ip bgp paths command:
Router# show ip bgp paths
Address Hash Refcount Metric Path
0x297A9C 0 2 0 i
0x30BF84 1 0 0 702 701 ?
0x2F7BC8 2 235 0 ?
0x2FA1D8 3 0 0 702 701 i
Table 17-5 describes significant fields shown in the display.
| Field | Description |
|---|---|
Address | Internal address where the path is stored. |
Hash | Hash bucket where path is stored. |
Refcount | Number of routes using that path. |
Metric | The MULTI_EXIT_DISC metric for the path. (The name of this metric for BGP versions 2 and 3 is INTER_AS.) |
Path | The AS_PATH for that route, followed by the origin code for that route. |
Use the show ip bgp regexp privileged EXEC command to display routes matching the regular expression.
show ip bgp regexp regular-expression
regular-expression | Regular-expression to match the BGP autonomous system paths |
Privileged EXEC
Router# show ip bgp regexp 108$
BGP table version is 1738, local router ID is 198.92.72.24
Status codes: s suppressed, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* 198.92.0.0 198.92.72.30 0 109 108 ?
* 198.92.1.0 198.92.72.30 0 109 108 ?
* 198.92.11.0 198.92.72.30 0 109 108 ?
* 198.92.14.0 198.92.72.30 0 109 108 ?
* 198.92.15.0 198.92.72.30 0 109 108 ?
* 198.92.16.0 198.92.72.30 0 109 108 ?
* 198.92.17.0 198.92.72.30 0 109 108 ?
* 198.92.18.0 198.92.72.30 0 109 108 ?
* 198.92.19.0 198.92.72.30 0 109 108 ?
* 198.92.24.0 198.92.72.30 0 109 108 ?
* 198.92.29.0 198.92.72.30 0 109 108 ?
* 198.92.30.0 198.92.72.30 0 109 108 ?
* 198.92.33.0 198.92.72.30 0 109 108 ?
* 198.92.35.0 198.92.72.30 0 109 108 ?
* 198.92.36.0 198.92.72.30 0 109 108 ?
* 198.92.37.0 198.92.72.30 0 109 108 ?
* 198.92.38.0 198.92.72.30 0 109 108 ?
* 198.92.39.0 198.92.72.30 0 109 108 ?
Use the show ip bgp summary EXEC command to display the status of all BGP connections.
show ip bgp summaryThis command has no arguments or keywords.
EXEC
The following is sample output from the show ip bgp summary command:
Router# show ip bgp summary
BGP table version is 717029, main routing table version 717029
19073 network entries (37544 paths) using 3542756 bytes of memory
691 BGP path attribute entries using 57200 bytes of memory
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State
193.0.16.1 4 1755 32642 2973 717029 0 0 1:27:11
193.0.17.1 4 1755 4790 2973 717029 0 0 1:27:51
193.0.18.1 4 1755 7722 3024 717029 0 0 1:28:13
193.0.19.1 4 1755 0 0 0 0 0 2d02 Active
193.0.20.1 4 1755 3673 3049 717029 0 0 2:50:10
193.0.21.1 4 1755 3741 3048 717029 0 0 12:24:43
193.0.22.1 4 1755 33129 3051 717029 0 0 12:24:48
193.0.23.1 4 1755 0 0 0 0 0 2d02 Active
193.0.24.1 4 1755 0 0 0 0 0 2d02 Active
193.0.25.1 4 1755 0 0 0 0 0 2d02 Active
193.0.26.1 4 1755 0 0 0 0 0 2d02 Active
193.0.27.1 4 1755 4269 3049 717029 0 0 12:39:33
193.0.28.1 4 1755 3037 3050 717029 0 0 2:08:15
198.92.72.24 4 1878 11635 13300 717028 0 0 0:50:39
Table 17-6 describes significant fields shown in the display.
| Field | Description |
|---|---|
BGP table version | Internal version number of BGP database. |
main routing table version | Indicates last version of BGP database that was injected into main routing table. |
Neighbor | IP address of a neighbor. |
V | Indicates BGP version number spoken to that neighbor. |
MsgRcvd | BGP messages received from that neighbor. |
MsgSent | BGP messages sent to that neighbor. |
TblVer | Last version of the BGP database that was sent to that neighbor. |
InQ | Number of messages from that neighbor waiting to be processed. |
OutQ | Number of messages waiting to be sent to that neighbor. |
Update/State | The length of time that the BGP session has been in state Established, or the current state if it is not Established. |
Use the show ip egp EXEC command to display statistics on EGP connections and neighbors.
show ip egpThis command has no arguments or keywords.
EXEC
The following is sample output from the show ip egp command:
Router# show ip egp
Local autonomous system is 109
EGP Neighbor FAS/LAS State SndSeq RcvSeq Hello Poll j/k Flags
10.3.0.27 1/109 IDLE 625 61323 60 180 0 Perm, Act
* 10.2.0.37 1/109 UP 12:29 250 14992 60 180 3 Perm, Act
* 10.7.0.63 1/109 UP 1d19 876 10188 60 180 4 Perm, Pass
Table 17-7 describes the fields shown in the display.
| Field | Description |
|---|---|
EGP Neighbor | Address of the EGP neighbor. |
FAS | Foreign autonomous system number. |
LAS | Local autonomous system number. |
State | State of the connection between peers. |
SndSeq | Send sequence number. |
RcvSeq | Receive sequence number. |
Hello | Interval between Hello/I-Heard-You packets. |
Poll | Interval between Poll/Update packets. |
j/k | Measure of reachability; 4 is perfect. |
Flags | Perm---Permanent. Temp---Temporary (neighbor will be removed). Act---Active, controlling the connection. Pass---Passive, neighbor controls the connection. |
Use the show ip irdp EXEC command to display IRDP values.
show ip irdpThis command has no arguments or keywords.
EXEC
The following is sample output from the show ip irdp command:
Router# show ip irdp
Ethernet 0 has router discovery enabled
Advertisements will occur between every 450 and 600 seconds.
Advertisements are valid for 1800 seconds.
Default preference will be 100.
--More--
Serial 0 has router discovery disabled
--More--
Ethernet 1 has router discovery disabled
As the display shows, show ip irdp output indicates whether or not router discovery has been configured for each router interface, and lists the values of router discovery configurables for those interfaces on which router discovery has been enabled. Explanations for the less self-evident lines of output in the display follow.
Advertisements will occur between every 450 and 600 seconds.
Indicates the configured minimum and maximum advertising interval for the interface.
Advertisements are valid for 1800 seconds.
Indicates the configured holdtime values for the interface.
Default preference will be 100.
Indicates the configured (or in this case default) preference value for the interface.
process-id | (Optional) Specifies a process ID. If this argument is included, only information for the specified routing process is included. |
EXEC
The following is sample output from the show ip ospf command when entered without a specific OSPF process ID:
Router# show ip ospf
Routing Process "ospf 201" with ID 192.42.110.200
Supports only single TOS(TOS0) route
It is an area border and autonomous system boundary router
Summary Link update interval is 0:30:00 and the update due in 0:16:26
External Link update interval is 0:30:00 and the update due in 0:16:27
Redistributing External Routes from,
igrp 200 with metric mapped to 2, includes subnets in redistribution
rip with metric mapped to 2
igrp 2 with metric mapped to 100
igrp 32 with metric mapped to 1
Number of areas in this router is 3
Area 192.42.110.0
Number of interfaces in this area is 1
Area has simple password authentication
SPF algorithm executed 6 times
Area ranges are
Link State Update Interval is 0:30:00 and due in 0:16:55
Link State Age Interval is 0:20:00 and due in 0:06:55
Table 17-8 describes significant fields shown in the display.
| Field | Description |
|---|---|
Routing process "ospf 201" with ID 192.42.110.200 | Process ID and OSPF router ID. |
Type of Service | Number of Types of Service supported (Type 0 only). |
Type of OSPF Router | Possible types are internal, area border, or autonomous system boundary. |
Summary Link update interval | Specify summary update interval in hours:minutes:seconds, and time to next update. |
External Link update interval | Specify external update interval in hours:minutes:seconds, and time to next update. |
Redistributing External Routes from | Lists of redistributed routes, by protocol. |
Number of areas | Number of areas in router, area addresses, and so on. |
Link State Update Interval | Specify router and network link state update interval in hours:minutes:seconds, and time to next update. |
Link State Age Interval | Specify max-aged update deletion interval and time until next database cleanup in hours:minutes:seconds. |
Use the show ip ospf border-routers privileged EXEC command to display the internal OSPF routing table entries to an Area Border Router (ABR) and Autonomous System Boundary Router (ASBR).
show ip ospf borders-routersThis command has no arguments or keywords.
Privileged EXEC
The following is sample output from the show ip ospf border-routers command:
Router# show ip ospf border-routers
OSPF Process 109 internal Routing Table
Destination Next Hop Cost Type Rte Type Area SPF No
160.89.97.53 144.144.1.53 10 ABR INTRA 0.0.0.3 3
160.89.103.51 160.89.96.51 10 ABR INTRA 0.0.0.3 3
160.89.103.52 160.89.96.51 20 ASBR INTER 0.0.0.3 3
160.89.103.52 144.144.1.53 22 ASBR INTER 0.0.0.3 3
Table 17-9 describes the fields shown in the display.
| Field | Description |
|---|---|
Destination | Destination's router ID. |
Next Hop | Next hop toward the destination. |
Cost | Cost of using this route. |
Type | The router type of the destination; it is either an Area Border Router (ABR) or Autonomous System Boundary Router (ASBR) or both. |
Rte Type | The type of this route, it is either an intra-area or interarea route. |
Area | The area ID of the area that this route is learned from. |
SPF No | The internal number of SPF calculation that installs this route. |
EXEC
process-id
| (Optional) Internally used identification parameter. It is locally assigned and can be any positive integer number. The number used here is the number assigned administratively when enabling the OSPF routing process. |
area-id
| (Optional) Area number associated with the OSPF address range defined in the network router configuration command used to define the particular area. |
link-state-id
| (Optional) Identifies the portion of the Internet environment that is being described by the advertisement. The value entered depends on the advertisement's LS type. It must be entered in the form of an IP address.
When the link state advertisement is describing a network, the link-state-id can take one of two forms: ---The network's IP address (as in type 3 summary link advertisements and in autonomous system external link advertisements). ---A derived address obtained from the link state ID. (Note that masking a network links advertisement's link state ID with the network's subnet mask yields the network's IP address.) When the link state advertisement is describing a router, the link state ID is always the described router's OSPF router ID. When an autonomous system external advertisement (LS Type = 5) is describing a default route, its link state ID is set to Default Destination (0.0.0.0). |
When entered with the optional keywords router, network, summary, asb-summary, and external, different displays result. Examples and brief descriptions of each form follow.
The following is sample output from the show ip ospf database command when no optional arguments or keywords are used:
Router# show ip ospf database
OSPF Router with id(190.20.239.66) (Autonomous system 300)
Displaying Router Link States(Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum Link count
155.187.21.6 155.187.21.6 1731 0x80002CFB 0x69BC 8
155.187.21.5 155.187.21.5 1112 0x800009D2 0xA2B8 5
155.187.1.2 155.187.1.2 1662 0x80000A98 0x4CB6 9
155.187.1.1 155.187.1.1 1115 0x800009B6 0x5F2C 1
155.187.1.5 155.187.1.5 1691 0x80002BC 0x2A1A 5
155.187.65.6 155.187.65.6 1395 0x80001947 0xEEE1 4
155.187.241.5 155.187.241.5 1161 0x8000007C 0x7C70 1
155.187.27.6 155.187.27.6 1723 0x80000548 0x8641 4
155.187.70.6 155.187.70.6 1485 0x80000B97 0xEB84 6
Displaying Net Link States(Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum
155.187.1.3 192.20.239.66 1245 0x800000EC 0x82E
Displaying Summary Net Link States(Area 0.0.0.0)
Link ID ADV Router Age Seq# Checksum
155.187.240.0 155.187.241.5 1152 0x80000077 0x7A05
155.187.241.0 155.187.241.5 1152 0x80000070 0xAEB7
155.187.244.0 155.187.241.5 1152 0x80000071 0x95CB
Table 17-10 describes significant fields shown in the display.
| Field | Description |
|---|---|
Link ID | Router ID number. |
ADV Router | Advertising router's router ID. |
Age | Link state age. |
Seq# | Link state sequence number (detects old or duplicate link state advertisements). |
Checksum | Fletcher checksum of the complete contents of the link state advertisement. |
Link count | Number of interfaces detected for router. |
The following is sample output from the show ip ospf database asb-summary command when no optional arguments are specified:
Router# show ip ospf database asb-summary
OSPF Router with id(190.20.239.66) (Autonomous system 300)
Displaying Summary ASB Link States(Area 0.0.0.0)
LS age: 1463
Options: (No TOS-capability)
LS Type: Summary Links(AS Boundary Router)
Link State ID: 155.187.245.1 (AS Boundary Router address)
Advertising Router: 155.187.241.5
LS Seq Number: 80000072
Checksum: 0x3548
Length: 28
Network Mask: 0.0.0.0 TOS: 0 Metric: 1
Table 17-11 describes significant fields shown in the display.
| Field | Description |
|---|---|
Router ID | Router ID number. |
Autonomous system | OSPF autonomous system number (OSPF process ID). |
LS age | Link state age. |
Options | Type of Service options (Type 0 only). |
LS Type | Link state type. |
Link State ID | Link state ID (autonomous system boundary router). |
Advertising Router | Advertising router's router ID. |
LS Seq Number | Link state sequence (detects old or duplicate link state advertisements). |
Checksum | LS checksum (Fletcher checksum of the complete contents of the link state advertisement). |
Length | Length in bytes of the link state advertisement. |
Network Mask | Network mask implemented. |
TOS | Type of Service. |
Metric | Link state metric. |
The following is sample output from the show ip ospf database external command when no optional arguments are specified:
Router# show ip ospf database external
OSPF Router with id(190.20.239.66) (Autonomous system 300)
Displaying AS External Link States
LS age: 280
Options: (No TOS-capability)
LS Type: AS External Link
Link State ID: 143.105.0.0 (External Network Number)
Advertising Router: 155.187.70.6
LS Seq Number: 80000AFD
Checksum: 0xC3A
Length: 36
Network Mask: 255.255.0.0
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 1
Forward Address: 0.0.0.0
External Route Tag: 0
Table 17-12 describes significant fields shown in the display.
| Field | Description |
|---|---|
Router ID | Router ID number. |
Autonomous system | OSPF autonomous system number (OSPF process ID). |
LS age | Link state age. |
Options | Type of Service options (Type 0 only). |
LS Type | Link state type. |
Link State ID | Link state ID (External Network Number). |
Advertising Router | Advertising router's router ID. |
LS Seq Number | Link state sequence number (detects old or duplicate link state advertisements). |
Checksum | LS checksum (Fletcher checksum of the complete contents of the link state advertisement). |
Length | Length in bytes of the link state advertisement. |
Network Mask | Network mask implemented. |
Metric Type | External Type. |
TOS | Type of Service. |
Metric | Link state metric. |
Forward Address | Forwarding address. Data traffic for the advertised destination will be forwarded to this address. If the forwarding address is set to 0.0.0.0, data traffic will be forwarded instead to the advertisement's originator. |
External Route Tag | External route tag, a 32-bit field attached to each external route. This is not used by the OSPF protocol itself. |
The following is sample output from the show ip ospf database network command when no optional arguments are specified:
Router# show ip ospf database network
OSPF Router with id(190.20.239.66) (Autonomous system 300)
Displaying Net Link States(Area 0.0.0.0)
LS age: 1367
Options: (No TOS-capability)
LS Type: Network Links
Link State ID: 155.187.1.3 (address of Designated Router)
Advertising Router: 190.20.239.66
LS Seq Number: 800000E7
Checksum: 0x1229
Length: 52
Network Mask: 255.255.255.0
Attached Router: 190.20.239.66
Attached Router: 155.187.241.5
Attached Router: 155.187.1.1
Attached Router: 155.187.54.5
Attached Router: 155.187.1.5
Table 17-13 describes significant fields shown in the display.
| Field | Description |
|---|---|
OSPF Router with ID(190.20.239.66) | Router ID number. |
Autonomous system 300 | OSPF autonomous system number (OSPF process ID). |
LS age: 1367 | Link state age. |
Options: (No TOS-capability) | Type of Service options (Type 0 only). |
LS Type: Network Links | Link state type. |
Link State ID | Link state ID of designated router. |
Advertising Router | Advertising router's router ID. |
LS Seq Number | Link state sequence (detects old or duplicate link state advertisements). |
Checksum | LS checksum (Fletcher checksum of the complete contents of the link state advertisement). |
Network Mask | Network mask implemented. |
AS Boundary Router | Definition of router type. |
Other fields | List of routers attached to the network, by IP address. |
The following is sample output from the show ip ospf database router command when no optional arguments are specified:
Router# show ip ospf database router
OSPF Router with id(190.20.239.66) (Autonomous system 300)
Displaying Router Link States(Area 0.0.0.0)
LS age: 1176
Options: (No TOS-capability)
LS Type: Router Links
Link State ID: 155.187.21.6
Advertising Router: 155.187.21.6
LS Seq Number: 80002CF6
Checksum: 0x73B7
Length: 120
AS Boundary Router
155 Number of Links: 8
Link connected to: another Router (point-to-point)
(link ID) Neighboring Router ID: 155.187.21.5
(Link Data) Router Interface address: 155.187.21.6
Number of TOS metrics: 0
TOS 0 Metrics: 2
Table 17-14 describes significant fields shown in the display.
| Field | Description |
|---|---|
Router ID | Router ID number. |
Autonomous system | OSPF autonomous system number (OSPF process ID). |
LS age | Link state age. |
Options | Type of Service options (Type 0 only). |
LS Type | Link state type. |
Link State ID | Link state ID. |
Advertising Router | Advertising router's router ID. |
LS Seq Number | Link state sequence (detects old or duplicate link state advertisements). |
Checksum | LS checksum (Fletcher checksum of the complete contents of the link state advertisement). |
Length | Length in bytes of the link state advertisement. |
AS Boundary Router | Definition of router type. |
Number of Links | Number of active links. |
link ID | Link type. |
Link Data | Router interface address. |
TOS | Type of Service metric (Type 0 only). |
The following is sample output from show ip ospf database summary command when no optional arguments are specified:
Router# show ip ospf database summary
OSPF Router with id(190.20.239.66) (Autonomous system 300)
Displaying Summary Net Link States(Area 0.0.0.0)
LS age: 1401
Options: (No TOS-capability)
LS Type: Summary Links(Network)
Link State ID: 155.187.240.0 (summary Network Number)
Advertising Router: 155.187.241.5
LS Seq Number: 80000072
Checksum: 0x84FF
Length: 28
Network Mask: 255.255.255.0 TOS: 0 Metric: 1
Table 17-15 describes significant fields shown in the display.
| Field | Description |
|---|---|
Router ID | Router ID number. |
Autonomous system | OSPF autonomous system number (OSPF process ID). |
LS age | Link state age. |
Options | Type of Service options (Type 0 only). |
LS Type | Link state type. |
Link State ID | Link state ID (summary network number). |
Advertising Router | Advertising router's router ID. |
LS Seq Number | Link state sequence (detects old or duplicate link state advertisements). |
Checksum | LS checksum (Fletcher checksum of the complete contents of the link state advertisement). |
Length | Length in bytes of the link state advertisement. |
Network Mask | Network mask implemented. |
TOS | Type of Service. |
Metric | Link state metric. |
Use the show ip ospf interface EXEC command to display OSPF-related interface information.
show ip ospf interface [interface-name]
interface-name | (Optional) Formed either as the one-word interface description (for example, serial0, ethernet0, or fddi1), or as the two-word interface-type unit-number specification (for example, serial 0, ethernet 1, or e 2). |
EXEC
The following is sample output from the show ip ospf interface command when Ethernet 0 is specified:
Router# show ip ospf interface ethernet 0
Ethernet 0 is up, line protocol is up
Internet Address 131.119.254.202, Mask 255.255.255.0, Area 0.0.0.0
AS 201, Router ID 192.77.99.1, Network Type BROADCAST, Cost: 10
Transmit Delay is 1 sec, State OTHER, Priority 1
Designated Router id 131.119.254.10, Interface address 131.119.254.10
Backup Designated router id 131.119.254.28, Interface addr 131.119.254.28
Timer intervals configured, Hello 10, Dead 60, Wait 40, Retransmit 5
Hello due in 0:00:05
Neighbor Count is 8, Adjacent neighbor count is 2
Adjacent with neighbor 131.119.254.28 (Backup Designated Router)
Adjacent with neighbor 131.119.254.10 (Designated Router)
Table 17-16 describes significant fields shown in the display.
| Field | Description |
|---|---|
Ethernet | Status of physical link and operational status of protocol. |
Internet Address | Interface IP address, subnet mask, and area address. |
AS | Autonomous system number (OSPF process ID), router ID, network type, link state cost. |
Transmit Delay | Transmit delay, interface state, and router priority. |
Designated Router | Designated router ID and respective interface IP address. |
Backup Designated router | Backup designated router ID and respective interface IP address. |
Timer intervals configured | Configuration of timer intervals. |
Hello | Number of seconds until next Hello packet is sent out this interface. |
Neighbor Count | Count of network neighbors and list of adjacent neighbors. |
Use the show ip ospf neighbor EXEC command to display OSPF-neighbor information on a per-interface basis.
show ip ospf neighbor [interface-name] [neighbor-id] detail
interface-name | (Optional) Formed either as the one-word interface description (for example, serial0, ethernet0, or fddi1), or as the two-word interface-type unit-number specification (for example, serial 0, ethernet 1, or e 2). |
neighbor-id | (Optional) Neighbor ID. |
detail | Display all neighbors given in detail (list all neighbors). |
EXEC
The following is sample output from the show ip ospf neighbor command showing a single line of summary information for each neighbor:
Router# show ip ospf neighbor
ID Pri State Dead Time Address Interface
199.199.199.137 1 FULL/DR 0:00:31 160.89.80.37 Ethernet0
192.31.48.1 1 FULL/DROTHER 0:00:33 192.31.48.1 Fddi0
192.31.48.200 1 FULL/DROTHER 0:00:33 192.31.48.200 Fddi0
199.199.199.137 5 FULL/DR 0:00:33 192.31.48.189 Fddi0
The following is sample output showing summary information about the neighbor that matches the Neighbor ID:
Router# show ip ospf neighbor 199.199.199.137
Neighbor 199.199.199.137, interface address 160.89.80.37
In the area 0.0.0.0 via interface Ethernet0
Neighbor priority is 1, State is FULL
Options 2
Dead timer due in 0:00:32
Link State retransmission due in 0:00:04
Neighbor 199.199.199.137, interface address 192.31.48.189
In the area 0.0.0.0 via interface Fddi0
Neighbor priority is 5, State is FULL
Options 2
Dead timer due in 0:00:32
Link State retransmission due in 0:00:03
If you specify the interface along with the Neighbor ID, the router displays the neighbors that match the Neighbor ID on the interface, as in the following sample display:
Router# show ip ospf neighbor e 0 199.199.199.137
Neighbor 199.199.199.137, interface address 160.89.80.37
In the area 0.0.0.0 via interface Ethernet0
Neighbor priority is 1, State is FULL
Options 2
Dead timer due in 0:00:37
Link State retransmission due in 0:00:04
You can also specify the interface without the Neighbor ID to show all neighbors on the specified interface, as in the following sample display:
Router# show ip ospf neighbor f 0
ID Pri State Dead Time Address Interface
192.31.48.1 1 FULL/DROTHER 0:00:33 192.31.48.1 Fddi0
192.31.48.200 1 FULL/DROTHER 0:00:32 192.31.48.200 Fddi0
199.199.199.137 5 FULL/DR 0:00:32 192.31.48.189 Fddi0
The following is sample output from the show ip ospf neighbor detail command:
Router# show ip ospf neighbor detail
Neighbor 160.89.96.54, interface address 160.89.96.54
In the area 0.0.0.3 via interface Ethernet0
Neighbor priority is 1, State is FULL
Options 2
Dead timer due in 0:00:38
Neighbor 160.89.103.52, interface address 160.89.103.52
In the area 0.0.0.0 via interface Serial0
Neighbor priority is 1, State is FULL
Options 2
Dead timer due in 0:00:31
Table 17-17 describes significant fields shown in the previous displays.
| Field | Description |
|---|---|
Neighbor x.x.x.x | Neighbor router ID. |
interface address x.x.x.x | IP address of the interface. |
In the area | Area and interface through which OSPF neighbor is known. |
Neighbor priority | Router priority of neighbor, neighbor state. |
State | OSPF state. |
Options | Hello packet options field contents (E-bit only; possible values are 0 and 2; 2 indicates area is not a stub; 0 indicates area is a stub. |
Dead timer | Expected time before router will declare neighbor dead. |
This command has no arguments or keywords.
EXEC
The information displayed by show ip ospf virtual-links is useful in debugging OSPF routing operations.
The following is sample output from the show ip ospf virtual-links command:
Router# show ip ospf virtual-links
Virtual Link to router 160.89.101.2 is up
Transit area 0.0.0.1, via interface Ethernet0, Cost of using 10
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 0:00:08
Adjacency State FULL
Table 17-18 describes significant fields shown in the display.
| Field | Description |
|---|---|
Virtual Link to router 160.89.101.2 is Up | Specifies the OSPF neighbor, and if the link to that neighbor is Up or Down. |
Transit area 0.0.0.1 | The transit area through which the virtual link is formed. |
via interface Ethernet0 | The interface through which the virtual link is formed. |
Cost of using 10 | The cost of reaching the OSPF neighbor through the virtual link. |
Transmit Delay is 1 sec | The transmit delay on the virtual link. |
State POINT_TO_POINT | The state of the OSPF neighbor. |
Timer intervals... | The various timer intervals configured for the link. |
Hello due in 0:00:08 | When the next Hello is expected from the neighbor. |
Adjacency State FULL | The adjacency state between the neighbors. |
This command has no arguments or keywords.
EXEC
The information displayed by show ip protocols is useful in debugging routing operations. Information in the Routing Information Sources field of the show ip protocols output can help you identify a router suspected of delivering bad routing information.
The following is sample output from the show ip protocols command, showing IGRP processes:
Router# show ip protocols
Routing Protocol is "igrp 109"
Sending updates every 90 seconds, next due in 44 seconds
Invalid after 270 seconds, hold down 280, flushed after 630
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Default networks flagged in outgoing updates
Default networks accepted from incoming updates
IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
IGRP maximum hopcount 100
IGRP maximum metric variance 1
Redistributing: igrp 109
Routing for Networks:
198.92.72.0
Routing Information Sources:
Gateway Distance Last Update
198.92.72.18 100 0:56:41
198.92.72.19 100 6d19
198.92.72.22 100 0:55:41
198.92.72.20 100 0:01:04
198.92.72.30 100 0:01:29
Distance: (default is 100)
Routing Protocol is "bgp 1878"
Sending updates every 60 seconds, next due in 0 seconds
Outgoing update filter list for all interfaces is 1
Incoming update filter list for all interfaces is not set
Redistributing: igrp 109
IGP synchronization is disabled
Automatic route summarization is enabled
Neighbor(s):
Address FiltIn FiltOut DistIn DistOut Weight RouteMap
192.108.211.17 1
192.108.213.89 1
198.6.255.13 1
198.92.72.18 1
198.92.72.19
198.92.84.17 1
Routing for Networks:
192.108.209.0
192.108.211.0
198.6.254.0
Routing Information Sources:
Gateway Distance Last Update
198.92.72.19 20 0:05:28
Distance: external 20 internal 200 local 200
Table 17-19 describes significant fields shown in the display.
| Field | Description |
|---|---|
Routing Protocol is "igrp 109" | Specifies the routing protocol used. |
Sending updates every 90 seconds | Specifies the time between sending updates. |
next due in 88 seconds | Precisely when the next update is due to be sent. |
Invalid after 270 seconds | Specifies the value of the invalid parameter. |
hold down for 280 | Specifies the current value of the hold-down parameter. |
flushed after 630 | Specifies the time in seconds after which the individual routing information will be thrown (flushed) out. |
Outgoing update ... | Specifies whether the outgoing filtering list has been set. |
Incoming update ... | Specifies whether the incoming filtering list has been set. |
Default networks | Specifies how these networks will be handled in both incoming and outgoing updates. |
IGRP metric | Specifies the value of the K0-K5 metrics as well as the maximum hopcount. |
Redistributing | Lists the protocol that is being redistributed. |
Routing | Specifies the networks that the routing process is currently injecting routes for. |
Routing Information Sources | Lists all the routing sources the router is using to build its routing table. For each source, you will see displayed:
|
The following is sample output from the show ip protocols command, showing IS-IS processes:
Router# show ip protocols
Routing Protocol is "isis"
Sending updates every 0 seconds
Invalid after 0 seconds, hold down 0, flushed after 0
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Redistributing: isis
Address Summarization:
None
Routing for Networks:
Serial0
Routing Information Sources:
Distance: (default is 115)
Use the show ip route EXEC command to display the current state of the routing table.
show ip route [address [mask]] | [protocol]
address | (Optional) Address about which routing information should be displayed. |
mask | (Optional) Argument for a subnet mask. |
protocol | (Optional) Name of a routing protocol; or the keyword connected, static, or summary. If you specify a routing protocol, use one of the following keywords: bgp, egp, eigrp, hello, igrp, isis, ospf, or rip. |
EXEC
The following is sample output from the show ip route command when entered without an address:
Router# show ip route
Codes: I - IGRP derived, R - RIP derived, O - OSPF derived
C - connected, S - static, E - EGP derived, B - BGP derived
* - candidate default route, IA - OSPF inter area route
E1 - OSPF external type 1 route, E2 - OSPF external type 2 route
Gateway of last resort is 131.119.254.240 to network 129.140.0.0
O E2 150.150.0.0 [160/5] via 131.119.254.6, 0:01:00, Ethernet2
E 192.67.131.0 [200/128] via 131.119.254.244, 0:02:22, Ethernet2
O E2 192.68.132.0 [160/5] via 131.119.254.6, 0:00:59, Ethernet2
O E2 130.130.0.0 [160/5] via 131.119.254.6, 0:00:59, Ethernet2
E 128.128.0.0 [200/128] via 131.119.254.244, 0:02:22, Ethernet2
E 129.129.0.0 [200/129] via 131.119.254.240, 0:02:22, Ethernet2
E 192.65.129.0 [200/128] via 131.119.254.244, 0:02:22, Ethernet2
E 131.131.0.0 [200/128] via 131.119.254.244, 0:02:22, Ethernet2
E 192.75.139.0 [200/129] via 131.119.254.240, 0:02:23, Ethernet2
E 192.16.208.0 [200/128] via 131.119.254.244, 0:02:22, Ethernet2
E 192.84.148.0 [200/129] via 131.119.254.240, 0:02:23, Ethernet2
E 192.31.223.0 [200/128] via 131.119.254.244, 0:02:22, Ethernet2
E 192.44.236.0 [200/129] via 131.119.254.240, 0:02:23, Ethernet2
E 140.141.0.0 [200/129] via 131.119.254.240, 0:02:22, Ethernet2
E 141.140.0.0 [200/129] via 131.119.254.240, 0:02:23, Ethernet2
The following is sample output that includes some IS-IS Level 2 routes learned:
Router# show ip route
Codes: I - IGRP derived, R - RIP derived, O - OSPF derived
C - connected, S - static, E - EGP derived, B - BGP derived
i - IS-IS derived
* - candidate default route, IA - OSPF inter area route
E1 - OSPF external type 1 route, E2 - OSPF external type 2 route
L1 - IS-IS level-1 route, L2 - IS-IS level-2 route
Gateway of last resort is not set
160.89.0.0 is subnetted (mask is 255.255.255.0), 3 subnets
C 160.89.64.0 255.255.255.0 is possibly down,
routing via 0.0.0.0, Ethernet0
i L2 160.89.67.0 [115/20] via 160.89.64.240, 0:00:12, Ethernet0
i L2 160.89.66.0 [115/20] via 160.89.64.240, 0:00:12, Ethernet0
Table 17-20 describes significant fields shown in these two displays.
| Field | Description |
|---|---|
O | Indicates protocol that derived the route. Possible values include:
|
E2 | Type of route. Possible values include:
|
150.150.0.0 | Indicates the address of the remote network. |
[160/5] | The first number in the brackets is the administrative distance of the information source; the second number is the metric for the route. |
via 131.119.254.6 | Specifies the address of the next router to the remote network. |
0:01:00 | Specifies the last time the route was updated in hours:minutes:seconds. |
Ethernet 2 | Specifies the interface through which the specified network can be reached. |
When you specify that you want information about a specific network displayed, more detailed statistics are shown. The following is sample output from the show ip route command when entered with the address 131.119.0.0.
Router# show ip route 131.119.0.0
Routing entry for 131.119.0.0 (mask 255.255.0.0)
Known via "igrp 109", distance 100, metric 10989
Tag 0
Redistributing via igrp 109
Last update from 131.108.35.13 on TokenRing0, 0:00:58 ago
Routing Descriptor Blocks:
* 131.108.35.13, from 131.108.35.13, 0:00:58 ago, via TokenRing0
Route metric is 10989, traffic share count is 1
Total delay is 45130 microseconds, minimum bandwidth is 1544 Kbit
Reliability 255/255, minimum MTU 1500 bytes
Loading 2/255, Hops 4
Table 17-21 describes significant fields shown in the display.
| Field | Description |
|---|---|
Routing entry for 131.119.0.0 (mask 255.255.0.0) | Network number and mask. |
Known via "igrp 109" | Indicates how the route was derived. |
distance 100 | Administrative distance of the information source. |
Tag 0 | Integer that is used to implement the route. |
Redistributing via igrp 109 | Indicates redistribution protocol. |
Last update from 131.108.35.13 on TokenRing0 | Indicates the IP address of a router that is the next hop to the remote network and the router interface on which the last update arrived. |
0:00:58 ago | Specifies the last time the route was updated in hours:minutes:seconds. |
131.108.35.13, from 131.108.35.13, 0:00:58 ago | Indicates the next hop address, the address of the gateway that sent the update, and the time that has elapsed since this update was received in hours:minutes:seconds. |
via TokenRing0 | Interface for this route. |
Route metric is 10989 | This value is the best metric for this routing descriptor block. |
traffic share count is 1 | Number of uses for this routing descriptor block. |
Total delay is 45130 microseconds | Total propagation delay in microseconds. |
minimum bandwidth is 1544 Kbit | Minimum bandwidth encountered when transmitting data along this route. |
Reliability 255/255 | Likelihood of successful packet transmission expressed as a number between 0 and 255 (255 is 100% reliability). |
minimum MTU 1500 bytes | Smallest MTU along the path. |
Loading 2/255 | Effective bandwidth of the route in kilobits per second/255 is saturation. |
Hops 4 | Hops to the destination or to the router where the route first enters IGRP. |
A dagger () indicates that the command is documented in another chapter.
show interfaces tunnel
show ip route summary
Use the show ip route summary EXEC command to display the current state of the routing table.
show ip route summaryThis command has no arguments or keywords.
EXEC
The following is sample output from the show ip route summary command:
Router# show ip route summary
Route Source Networks Subnets Overhead Memory (bytes)
connected 0 3 126 360
static 1 2 126 360
igrp 109 747 12 31878 91080
internal 3 360
Total 751 17 32130 92160
Router#
Table 17-22 describes the fields shown in the display:
| Field | Description |
|---|---|
Route Source | Routing protocol name, or connected, static, or internal. |
Networks | The number of Class A, B, or C networks that are present in the routing table for each route source. |
Subnets | The number of subnets that are present in the routing table for each route source, including host routes. |
Overhead | Any additional memory involved in allocating the routes for the particular route source other than the memory specified under "Memory." |
Memory | The number of bytes allocated to maintain all the routes for the particular route source. |
show ip route
Use the show ip route supernets-only privileged EXEC command to display information about supernets.
show ip route supernets-onlyPrivileged EXEC
The following is sample output from the show ip route supernets-only command:
Router# show ip route supernets-only
Codes: I - IGRP derived, R - RIP derived, O - OSPF derived
C - connected, S - static, E - EGP derived, B - BGP derived
i - IS-IS derived, D - EIGRP derived
* - candidate default route, IA - OSPF inter area route
E1 - OSPF external type 1 route, E2 - OSPF external type 2 route
L1 - IS-IS level-1 route, L2 - IS-IS level-2 route
EX - EIGRP external route
Gateway of last resort is not set
B 198.92.0.0 (mask is 255.255.0.0) [20/0] via 198.92.72.30, 0:00:50
B 192.0.0.0 (mask is 255.0.0.0) [20/0] via 198.92.72.24, 0:02:50
Router#
This display shows supernets only; it does not show subnets.
The show isis database EXEC command displays the IS-IS link state database.
show isis database [level-1] [level-2] [l1] [l2] [detail] [lspid]
level-1 | (Optional) Displays the IS-IS link state database for Level 1. |
level-2 | (Optional) Displays the IS-IS link state database for Level 2. |
l1 | (Optional) Abbreviation for the option level-1. |
l2 | (Optional) Abbreviation for the option level-2. |
detail | (Optional) When specified, the contents of each LSP is displayed. Otherwise, a summary display is provided. |
lspid | (Optional) Link-state protocol ID. When specified, the contents of a single LSP is displayed by its ID number. |
EXEC
Each of the options shown in brackets for this command can be entered in an arbitrary string within the same command entry. For example, the following are both valid command specifications and provide the same output: show isis database detail l2 and show isis database l2 detail.
The following is sample output from the show isis database command when it is specified with no options or as show isis database l1 l2:
Router# show isis database
IS-IS Level-1 Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0C00.0C35.00-00 0x0000000C 0x5696 792 0/0/0
0000.0C00.40AF.00-00* 0x00000009 0x8452 1077 1/0/0
0000.0C00.62E6.00-00 0x0000000A 0x38E7 383 0/0/0
0000.0C00.62E6.03-00 0x00000006 0x82BC 384 0/0/0
0800.2B16.24EA.00-00 0x00001D9F 0x8864 1188 1/0/0
0800.2B16.24EA.01-00 0x00001E36 0x0935 1198 1/0/0
IS-IS Level-2 Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0C00.0C35.03-00 0x00000005 0x04C8 792 0/0/0
0000.0C00.3E51.00-00 0x00000007 0xAF96 758 0/0/0
0000.0C00.40AF.00-00* 0x0000000A 0x3AA9 1077 0/0/0
Table 17-23 describes significant fields shown in the display.
| Field | Description |
|---|---|
LSPID | The link state PDU ID. The first six octets form the System ID. The next octet is the pseudo ID. When this value is zero, the LSP describes links from the system. When it is nonzero, the LSP is a pseudonode LSP. The designated router for an interface is the only system that originates pseudonode LSPs. The last octet is the LSP number. If there is more data than can fit in a single LSP, additional LSPs are sent with increasing LSP numbers. An asterisk (*) indicates that the LSP was originated by the local system. |
LSP Seq Num | Sequence number for the LSP that allows other systems to determine if they have received the latest information from the source. |
LSP Checksum | Checksum of the entire LSP packet. |
LSP Holdtime | Amount of time the LSP remains valid, in seconds. |
ATT | The attach bit. This indicates that the router is also a Level 2 router, and it can reach other areas. |
P | The P bit. Detects if the IS is area partition repair capable. |
OL | The Overload bit. Determines if the IS is congested. |
The following is sample output from the show isis database detail command.
Router# show isis database detail
IS-IS Level-1 Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0C00.0C35.00-00 0x0000000C 0x5696 325 0/0/0
Area Address: 47.0004.004D.0001
Area Address: 39.0001
Metric: 10 IS 0000.0C00.62E6.03
Metric: 0 ES 0000.0C00.0C35
--More--
0000.0C00.40AF.00-00* 0x00000009 0x8452 608 1/0/0
Area Address: 47.0004.004D.0001
Metric: 10 IS 0800.2B16.24EA.01
Metric: 10 IS 0000.0C00.62E6.03
Metric: 0 ES 0000.0C00.40AF
IS-IS Level-2 Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0C00.0C35.03-00 0x00000005 0x04C8 317 0/0/0
Metric: 0 IS 0000.0C00.0C35.00
--More--
0000.0C00.3E51.00-00 0x00000009 0xAB98 1182 0/0/0
Area Address: 39.0004
Metric: 10 IS 0000.0C00.40AF.00
Metric: 10 IS 0000.0C00.3E51.05
As the output shows, in addition to the information displayed with show isis database, the show isis database detail command displays the contents of each LSP.
Table 17-24 describes significant fields shown in the display.
| Field | Description |
|---|---|
LSPID | The link state PDU ID. The first six octets form the System ID. The next octet is the pseudo ID. When this value is zero, the LSP describes links from the system. When it is nonzero, the LSP is a pseudonode LSP. The designated router for an interface is the only system that originates pseudonode LSPs. The last octet is the LSP number. If there is more data than can fit in a single LSP, additional LSPs are sent with increasing LSP numbers. An asterisk (*) indicates that the LSP was originated by the local system. |
LSP Seq Num | Sequence number for the LSP that allows other systems to determine if they have received the latest information from the source. |
LSP Checksum | Checksum of the entire LSP packet. |
LSP Holdtime | Amount of time the LSP remains valid, in seconds. |
ATT | The attach bit. This indicates that the router is also a Level 2 router, and it can reach other areas. |
P | The P bit. Detects if the IS is area partition repair capable. |
OL | The Overload bit. Determines if the IS is congested. |
Area Address: | Reachable area addresses from the router. |
Metric: | IS-IS metric for the route. |
The following is additional sample output from the show isis database detail command.This is a Level 2 LSP. The area address 39.0001 is the address of the area in which the router resides.
Router# show isis database detail l2
IS-IS Level-2 Link State Database
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0C00.1111.00-00* 0x00000006 0x4DB3 1194 0/0/0
Area Address: 39.0001
NLPID: 0x81 0xCC
IP Address: 160.89.64.17
Metric: 10 IS 0000.0C00.1111.09
Metric: 10 IS 0000.0C00.1111.08
Metric: 10 IP 160.89.65.0 255.255.255.0
Metric: 10 IP 160.89.64.0 255.255.255.0
Metric: 0 IP-External 10.0.0.0 255.0.0.0
Table 17-25 describes significant fields shown in the display.
| Field | Description |
|---|---|
LSPID | The link state PDU ID. The first six octets form the System ID. The next octet is the pseudo ID. When this value is zero, the LSP describes links from the system. When it is nonzero, the LSP is a pseudonode LSP. The designated router for an interface is the only system that originates pseudonode LSPs. The last octet is the LSP number. If there is more data than can fit in a single LSP, additional LSPs are sent with increasing LSP numbers. An asterisk (*) indicates that the LSP was originated by the local system. |
LSP Seq Num | Sequence number for the LSP that allows other systems to determine if they have received the latest information from the source. |
LSP Checksum | Checksum of the entire LSP packet. |
LSP Holdtime | Amount of time the LSP remains valid, in seconds. |
ATT | The attach bit. This indicates that the router is also a Level 2 router, and it can reach other areas. |
P | The P bit. Detects if the IS is area partition repair capable. |
OL | The Overload bit. Determines if the IS is congested. |
Area Address: | Reachable area addresses from the router. |
NLPID | Indicates that both IP and OSI (0x0cc and 0x081 respectively) are supported in IS-IS for this router. |
IP Address: | The IP address for the router is advertised in the LSP. |
Metric: | IS-IS metric for the route. |
Various addresses | The "IP" entries are the directly connected IP subnets the router is advertising (with associated metrics). The "IP-External" is a redistribute route. |
Use the show route-map EXEC command to display all route-maps configured or only the one specified.
show route-map [map-name]
map-name | (Optional) Name of a specific route-map |
EXEC
The following is sample output from the show route-map command:
Router# show route-map
route-map foo, permit, sequence 10
Match clauses:
tag 1 2
Set clauses:
metric 5
route-map foo, permit, sequence 20
Match clauses:
tag 3 4
Set clauses:
metric 6
Table 17-26 describes the fields shown in the display:
| Field | Description |
|---|---|
route-map | Name of the route-map. |
permit | Indicates that the route is redistributed as controlled by the set actions. |
sequence | Number that indicates the position a new route map is to have in the list of route maps already configured with the same name. |
Match clauses | Match criteria---conditions under which redistribution is allowed for the current route-map. |
Set clauses | Set actions---the particular redistribution actions to perform if the criteria enforced by the match commands are met. |
redistribute
route-map
Use the summary-address router configuration command to create aggregate IS-IS addresses. The
no summary-address command restores the default.
address | Summary address designated for a range of addresses. |
mask | IP subnet mask used for the summary route. |
level-1 | If level-1 is specified, only routes redistributed into Level 1 are summarized with the configured address/mask value. |
level-1-2 | If specified, the summary router is injected into both a Level 1 area and a Level 2 subdomain. |
level-2 | If level-2 is specified, routes learned by Level 1 routing will be summarized into the Level 2 backbone with the configured address/mask value. |
Disabled
Router configuration
In the following configuration, summary address 10.1.0.0 includes address 10.1.1, 10.1.2, 10.1.3, 10.1.4, and so forth. Only the address 10.1.0.0 is advertised in an IS-IS Level 1 Link State PDU.
summary-address 10.1.0.0 255.255.0.0 level-1
Use the synchronization router configuration command to disable the synchronization between BGP and your IGP. The no synchronization command enables a router to advertise a network route without waiting for the IGP.
synchronizationThis command has no arguments or keywords.
Enabled
Router configuration
Usually, a BGP speaker does not advertise a route to an external neighbor unless that route is local or exists in the IGP. The no synchronization command allows a router to advertise a network route without waiting for the IGP. This feature allows routers within an autonomous system to have the route before BGP makes it available to other autonomous systems.
Use synchronization if there are routers in the autonomous system that do not speak BGP.
The following example enables the router to advertise a network route without waiting for the IGP:
router bgp 120
no synchronization
Use the table-map router configuration command to modify metric and tag values when the IP routing table is updated with BGP learned routes. Use the no form of the command to disable this function.
table-map route-map-name
route-map-name | Route map name, from the route-map command. |
Disabled
Router configuration
This command adds the route map name defined by the route-map command to the IP routing table. This command is used to set the tag name and the route metric to implement redistribution.
You can use match clauses of route maps in the table-map command. IP access list, AS paths, and next-hop match clauses are supported.
In the following example, the router is configured to automatically compute the tag value for the BGP learned routes and to update the IP routing table.
route-map tag
match as path 10
set automatic-tag
!
router bgp 100
table-map tag
match as-path
match ip address
match ip next-hop
route-map
Use the timers basic router configuration command to adjust EGP, RIP, or IGRP network timers. The no timers basic command restores the defaults.
timers basic update invalid holddown flush [sleeptime]
update | Rate (in seconds) at which updates are sent. This is the fundamental timing parameter of the routing protocol. |
invalid | Interval of time (in seconds) after which a route is declared invalid; it should be three times the value of update. A route becomes invalid when there is an absence of updates that refresh the route. The route then enters holddown. The route is marked inaccessible and advertised as unreachable. However, the route is still used for forwarding packets. |
holddown | Interval (in seconds) during which routing information regarding better paths is suppressed. It should be at least three times the value of update. A route enters into a holddown state when an update packet is received that indicates the route is unreachable. The route is marked inaccessible and advertised as unreachable. However, the route is still used for forwarding packets. When holddown expires, routes advertised by other sources are accepted and the route is no longer inaccessible. |
flush | Amount of time (in seconds) that must pass before the route is removed from the routing table; the interval specified must be at least the sum of invalid and holddown. If it is less than this sum, the proper holddown interval cannot elapse, which results in a new route being accepted before the holddown interval expires. |
sleeptime | (Optional) For IGRP only, interval (in milliseconds) for postponing routing updates in the event of a flash update. The sleeptime value should be less than the update time. If the sleeptime is greater than the update time, routing tables will become unsynchronized. |
| Protocol | update | invalid | holddown | flush | sleeptime |
|---|---|---|---|---|---|
EGP | N/A | 1080 | N/A | 1200 | N/A |
RIP | 30 | 180 | 180 | 240 | N/A |
IGRP | 90 | 270 | 280 | 630 | 0 |
Router configuration
The basic timing parameters for IGRP, EGP, and RIP are adjustable. Since these routing protocols are executing a distributed, asynchronous routing algorithm, it is important that these timers be the same for all routers in the network.
In the following example, updates are broadcast every 5 seconds. If a router is not heard from in 15 seconds, the route is declared unusable. Further information is suppressed for an additional 15 seconds. At the end of the suppression period, the route is flushed from the routing table.
router igrp 109
timers basic 5 15 15 30
Note that by setting a short update period, you run the risk of congesting slow-speed serial lines; however, this is not a big concern on faster-speed Ethernets and T1-rate serial lines. Also, if you have many routes in your updates, you can cause the routers to spend an excessive amount of time processing updates.
When the timers basic command is used with EGP, the update time and holddown time are ignored. For example, the commands that follow will set the invalid time for EGP to 100 seconds and the flush time to 200 seconds.
router egp 47
timers basic 0 100 0 200
Use the timers bgp router configuration command to adjust BGP network timers. The no timers bgp command resets the BGP timing defaults.
timers bgp keepalive holdtime
keepalive | Frequency, in seconds, with which the router sends keepalive messages to its peer. The default is 60 seconds. |
holdtime | Interval, in seconds, after not receiving a keepalive message that the router declares a peer dead. The default is 180 seconds. |
keepalive timer = 60 seconds
holdtime timer = 180 seconds
Router configuration
The following example changes the keepalive timer to 70 seconds and the holdtime timer to 210 seconds:
timers bgp 70 210
clear ip bgp
router bgp
show ip bgp
Use the timers egp router configuration command to adjust EGP Hello and polltime network timers. The no timers egp command resets the EGP timing defaults.
timers egp hello polltime
hello | Frequency, in seconds, with which the router sends Hello messages to its peer. The default is 60 seconds. |
polltime | Interval, in seconds, for how frequently to exchange updates. The default is 180 seconds. |
Hello timer = 60 seconds
polltime timer = 180 seconds
Router configuration
To change the invalid time or flush time for EGP routes, use the timers basic router configuration command.
The following example changes the EGP timers to 2 minutes and 5 minutes, respectively:
timers egp 120 300
router egp
show ip egp
timers basic
Use the traffic-share router configuration command to control how traffic is distributed among routes when there are multiple routes for the same destination network that have different costs. Use the no form of the command to disable this function.
traffic-share {balanced | min}
balanced | Distributes traffic proportionately to the ratios of the metrics. |
min | Uses routes that have minimum costs. |
Traffic is distributed proportionately to the ratios of the metrics.
Router configuration
This command applies to IGRP and enhanced IGRP routing protocols only. With the default setting, routes that have higher metrics represent less-preferable routes and get less traffic. Configuring traffic-share min causes the router to only divide traffic among the routes with the best metric. Other routes will remain in the routing table, but will receive no traffic.
In the following example, only routes of minimum cost will be used:
router igrp 5
traffic-share min
Use the validate-update-source router configuration command to cause the router to validate the source IP address of incoming routing updates for RIP and IGRP routing protocols. Use the no form of this command to disable this validate function for RIP or IGRP.
validate-update-sourceThis command has no arguments or keywords.
Enabled
Router configuration
This command is only applicable to RIP and IGRP. The router ensures that the source IP address of incoming routing updates is on the same IP network as one of the addresses defined for the receiving interface.
Disabling split horizon on the incoming interface will also cause the system to perform this validation check.
For unnumbered IP interfaces (interfaces configured as ip unnumbered), no checking is performed.
In the following example, the router is configured to not perform validation checks on the source IP address of incoming RIP updates:
router rip
network 128.105.0.0
no validate-update-source
Use the variance router configuration command to control load balancing in an IGRP-based internet. The no variance command resets variance to the default value.
variance multiplier
multiplier | Range of metric values that will be accepted for load balancing. Acceptable values are nonzero, positive integers. Default is 1. |
1, or equal-cost load balancing
Router configuration
Setting this value lets the router determine the feasibility of a potential route. A route is feasible if the next router in the path is closer to the destination than the current router and if the metric for the entire path is within the variance. Only paths that are feasible can be used for load balancing and included in the routing table.
If the following two conditions are met, the route is deemed feasible and can be added to the routing table:
1. The local best metric must be greater than the metric learned from the next router.
2. The multiplier times the local best metric for the destination must be greater than or equal to the metric through the next router.
The following example sets a variance value of 4:
router igrp 109
variance 4
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