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The Xerox Network Systems (XNS) protocols, which were developed by the Xerox Corporation, are designed to be used across a variety of communication media, processors, and office applications. Ungermann-Bass, Inc. (now a part of Tandem Computers) adopted XNS in developing its Net/One XNS routing protocol. Standard XNS routing uses the routing information protocol (RIP) update packets and the hop count metric. Ungermann-Bass Net/One uses hello packets and a path-delay metric.
This chapter describes the commands to configure both standard Xerox Network System (XNS) routing and Ungermann-Bass Net/One XNS routing. You can also configure our routers to interoperate with Ungermann-Bass routers. For XNS configuration information and examples, refer to the "Configuring XNS" chapter in the Router Products Configuration Guide.
To define a standard XNS access list, use the standard version of the access-list global configuration command. To remove a standard access list, use the no form of this command.
access-list access-list-number {deny | permit} source-network[.source-address
access-list-number | Number of the access list. This is a decimal number from 400 to 499. |
deny | Denies access if the conditions are matched. |
permit | Permits access if the conditions are matched. |
source-network | Number of the network from which the packet is being sent. This is a 32-bit decimal number. You can omit leading zeros. A network number of -1 matches all networks. Note that you enter the network number in decimal, and this number is expressed in decimal format in our configuration files and routing tables. However, the router internally converts the network number into hexadecimal. This means, for instance, that a network analyzer will display the network number in hexadecimal. |
source-address | (Optional) Host on source-network from which the packet is being sent. This is a 48-bit hexadecimal value represented as a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). |
source-address-mask | (Optional) Mask to be applied to source-address. This is a 48-bit value represented as a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). Place ones in the bit positions you want to mask. |
destination-network | (Optional) Number of the network to which the packet is being sent. This is a 32-bit decimal number. A network number of -1 matches all networks. You can omit leading from the network number. Note that you enter the network number in decimal, and this number is expressed in decimal format in our configuration files and routing tables. However, the router internally converts the network number into hexadecimal. This means, for instance, that a network analyzer will display the network number in hexadecimal. |
destination-address | (Optional) Host on destination-network to which the packet is being sent. This is a 48-bit hexadecimal value represented as a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). |
destination-address-mask | (Optional) Mask to be applied to destination-address. This is a 48-bit value represented as a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). Place ones in the bit positions you want to mask. |
None
Global configuration
Standard XNS access lists filter on the source network only. All other parameters are optional. This means that you cannot use them to prevent traffic from going to or coming from specific hosts.
Use the xns access-group command to assign an access list to an interface. You can apply only one extended or one standard access list to an interface. The access list filters all outgoing packets on the interface.
The following example denies access to packets from source network 1 that are destined for network 2. It permit all other traffic.
access-list 400 deny 1 2
access-list 400 permit -1 -1
The following example adds masks for the source and destination networks:
access-list 400 deny 1.0011.1622.0015 0000.0000.0000 2.301D3.020C.0022
0000.00ff.ffff
access-list 400 permit -1 0000.0000.0000 -1 0000.0000.0000
access-list (extended)
xns access-group
xns input-network-filter
To define an extended XNS access list, use the extended version of the access-list global configuration command. To remove an extended access list, use the no form of this command.
access-list access-list-number {deny | permit} protocol [source-network[.source-host
access-list-number | Number of the access list. This is a decimal number from 500 to 599. |
deny | Denies access if the conditions are matched. |
permit | Permits access if the conditions are matched. |
protocol | Number of an XNS protocol, in decimal. See the documentation accompanying your host's XNS implementation for a list of protocol numbers. |
source-network | (Optional) Number of the network from which the packet is being sent. This is a 32-bit decimal number. A network number of -1 matches all networks. You can omit leading from the network number. Note that you enter the network number in decimal, and this number is expressed in decimal format in our configuration files and routing tables. However, the router internally converts the network number into hexadecimal. This means, for instance, that a network analyzer will display the network number in hexadecimal. |
source-host | (Optional) Host on source-network from which the packet is being sent. This is a 48-bit hexadecimal value represented as a dotted triplet of 4-digit hexadecimal numbers (xxxx.xxxx.xxxx). |
source-network-mask | (Optional) Mask to be applied to source-network. The mask is a 32-bit decimal number. The mask must immediately be followed by a period, which must in turn immediately be followed by source-host-mask. |
source-host-mask | (Optional) Mask to be applied to source-host. This is a 48-bit value represented as a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). Place ones in the bit positions you want to mask. |
source-socket | Number of the socket from which the packet is being sent. This is a 16-bit decimal value. See the documentation accompanying your host's XNS implementation for a list of socket numbers. |
destination-network | (Optional) Number of the network to which the packet is being sent. This is a 32-bit decimal number. A network number of -1 matches all networks. You can omit leading from the network number. Note that you enter the network number in decimal, and this number is expressed in decimal format in our configuration files and routing tables. However, the router internally converts the network number into hexadecimal. This means, for instance, that a network analyzer will display the network number in hexadecimal. |
destination-host | (Optional) Host on destination-network to which the packet is being sent. This is a 48-bit hexadecimal value represented as a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). |
destination-network-mask | (Optional) Mask to be applied to destination-network. The mask is a 32-bit decimal number. The mask must immediately be followed by a period, which must in turn immediately be followed by destination-host-mask. |
destination-host-mask | (Optional) Mask to be applied to destination-host. This is a 48-bit value represented as a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). Place ones in the bit positions you want to mask. |
destination-socket | (Optional) Number of the socket to which the packet is being sent. This is a 16-bit decimal value. See the documentation accompanying your host's XNS implementation for a list of socket numbers. |
pep | (Optional) Packet Exchange Protocol type. PEP is a connectionless-oriented protocol that uses XNS Type 4 IDP frames. |
None
Global configuration
Extended XNS access lists filter on protocol type. All other parameters are optional.
Use the xns access-group command to assign an access list to an interface. You can apply only one extended or one standard access list to an interface. The access list filters all outgoing packets on the interface.
The following example shows two ways to allow protocol type 20 on any socket (from a certain make of machine [Cisco Ethernet]) on network 10 to access any hosts on networks 1000 through 1015 on any socket.
In the following example, the access-list commands were issued without using the network mask option.
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1000 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1001 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1002 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1003 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1004 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1005 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1006 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1007 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1008 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1009 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1010 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1011 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1012 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1013 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1014 0
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0 1015 0
In the following example, the access-list command performs the same operation, but in a much shorter time, because the netmask option is used.
access-list 505 permit 20 10.0000.0C00.0000 0000.0000.FFFF 0
1000.0000.0000.0000 15.FFFF.FFFF.FFFF 0
access-list (standard)
xns access-group
xns input-network-filter
To check host reachability and network connectivity, use the user ping EXEC command.
ping xns address
xns | Specifies the XNS protocol. |
address | Address of system to ping. |
EXEC
The user ping (packet internet groper function) command provides a basic ping facility for users who do not have system privileges. This command is equivalent to the nonverbose form of the privileged ping command. It sends five 100-byte ping packets.
The ping command works only on our network servers running Software Release 8.2 or later.
If the system cannot map an address for a host name, it will return an "%Unrecognized host or address" error message.
To abort a ping session, type the escape sequence. By default, this is Ctrl-^ X. You enter this by simultaneously pressing the Ctrl, Shift, and 6 keys, letting go, and then pressing the X key.
Table 21-1 describes the test characters displayed in ping responses.
The following display shows sample output from the XNS ping command:
router> ping xns 1.0000.0c01.f4cf
Type escape sequence to abort.
Sending 5, 100-byte XNS Echoes to 1.0000.0c01.f4cf, timeout is 2 seconds:
!!!!!
Success rate is 100 percent, round-trip min/avg/max = 4/5/12 ms
To check host reachability and network connectivity, use the ping privileged EXEC command.
pingThis command has no arguments or keywords.
Privileged EXEC
The privileged ping (packet internet groper function) command provides a complete ping facility for users who have system privileges.
If the system cannot map an address for a host name, it will return an "%Unrecognized host or address" error message.
To abort a ping session, type the escape sequence. By default, this is Ctrl-^ X. You enter this by simultaneously pressing the Ctrl, Shift, and 6 keys, letting go, and then pressing the X key.
Table 21-2 describes the test characters displayed in ping responses.
The following display shows sample input to and output from the ping command:
Router# ping
Protocol [ip]: xns
Target XNS address: 2001.aa00.0400.6508
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Verbose [n]:n
Type escape sequence to abort.
Sending 5, 100-byte XNS Echos to 2001.aa00.0400.6508, timeout is 2 seconds:
Success rate is 100 percent, round-trip min/avg/max = 4/5/12 ms
The following display shows sample input to and output from the XNS ping command in verbose mode. In this mode, the command shows the round-trip time, in milliseconds, for each XNS echo packet sent. In this display, the packets are labeled 0, 1, 2, 3, and 4.
Router# ping
Protocol [ip]: xns
Target XNS address: 2001.aa00.0400.6508
Repeat count [5]:
Datagram size [100]:
Timeout in seconds [2]:
Verbose [n]: y
Type escape sequence to abort.
Sending 5, 100-byte XNS Echos to 2001.aa00.0400.6508, timeout is 2 seconds:
0 in 12 ms
1 in 4 ms
2 in 4 ms
3 in 4 ms
4 in 4 ms
Success rate is 100 percent, round-trip min/avg/max = 4/5/12 ms
To display the contents of the XNS fast-switching cache, use the show xns cache EXEC command.
show xns cacheThis command has no arguments or keywords.
EXEC
The following is sample output from the show xns cache command:
Router# show xns cache
XNS routing cache version is 23
Destination Interface MAC Header
* 2.0000.00c0.1234 Ethernet1 000000C0123400000C00D8DB0600
Table 21-3 describes the fields shown in the display.
| Field | Description |
|---|---|
XNS routing cache version is 23 | Number identifying the fast-switching cache table. It increments each time the table changes. |
Destination | Destination network for this packet. Valid entries are marked by an asterisk (*). |
Interface | Router interface through which this packet is transmitted. |
MAC Header | First bytes of this packet's MAC header. |
To display the status of the XNS interfaces configured in the router and the parameters configured on each interface, use the show xns interface EXEC command.
show xns interface [type number]
type | (Optional) Interface type. It can be one of the following types: asynchronous, dialer, Ethernet (IEEE 802.3), loopback, null, serial, or tunnel. |
number | (Optional) Interface number. |
EXEC
The following is sample output from the show xns interface command:
Router# show xns interface
Ethernet 0 is up, line protocol is up
XNS address is 60.0000.0c00.1d23
xns encapsulation is ARPA
Helper address is 912.ffff.ffff.ffff
Outgoing address list is not set
Input filter list is not set
Output filter list is not set
Router filter list is not set
Update timer is not set
XNS fast-switching enabled
Ethernet 1 is administratively down, line protocol is down
XNS protocol processing disabled
Serial 1 is up, line protocol is up
XNS protocol processing disabled
Table 21-4 describes the fields shown in the display.
| Field | Description |
|---|---|
Ethernet 0 is up | Type of interface and whether it is currently active and inserted into the network (up) or inactive and not inserted (down). |
line protocol is up | Indicates whether the software processes that handle the line protocol believe that the interface is usable (that is, whether keepalives are successful). |
XNS address | Network and host number of the local router interface. |
xns encapsulation | Type of encapsulation configured on the interface. |
Helper address | Address of a target XNS server or network to which broadcast XNS packets are forwarded, as configured with the xns helper-address command. |
Outgoing address list | Indicates whether an access list has been enabled with the access-list command. |
Input filter list | Number of the input filter applied to the interface with the xns input-network-filter command. |
Output filter list | Number of the output filter applied to the interface with the xns output-network-filter command. |
Router filter list | Number of the router filter applied to the interface with the xns router-filter command. |
Update timer | How often the router sends RIP updates, as configured with the xns update-time command. |
XNS fast-switching | Indicates whether XNS fast switching is enabled (default) or disabled for this interface. |
administratively down | Hardware has been taken down by an administrator. |
access-list (standard)
access-list (standard)
xns helper-address
xns input-network-filter
xns output-network-filter
xns router-filter
xns update-time
To display the contents of the XNS routing table, use the show xns route EXEC command.
show xns route [network]
network | (Optional) Number of the network that the route is to. This is a 32-bit decimal number. You can omit leading zeros. |
EXEC
The following is sample output from the show xns route command:
Router# show xns route
Codes: R - RIP derived, C - connected, S - static, 1 learned routes
Maximum allowed path(s) are/is 1
C Net 14 is directly connected, 0 uses, Ethernet0
C Net 15 is directly connected, 0 uses, Ethernet1
R Net 16 [1/0] via 14.0000.0c00.3e3b, 10 sec, 0 uses, Ethernet0
Table 21-5 describes the fields shown in the display.
| Field | Description |
|---|---|
Codes | Codes defining how the route was learned. |
R | Route learned from a RIP update. |
C | Directly connected network. |
S | Statically defined route via the xns route command. |
learned routes | Number of routes learned from RIP updates. |
Maximum allowed paths | Maximum number of paths for which the router has been configured with the xns helper-address command. |
Net 14 | XNS network number. |
is directly connected | Indicates that the network is directly connected to the router. |
uses | Fair estimate of the number of times a route gets used. It actually indicates the number of times the route has been selected for use prior to operations such as access list filtering. |
Ethernet0 | Possible interface through which you can reach the remote network via the specified router. |
[1/0] | Delay/Metric. The delay is the delay between sending routing updates. The metric is the XNS metric used in making routing decisions. |
via | Address of a router that is the next hop to the remote network. |
sec | Number of seconds since information about this network was last heard. |
To display information about the number and type of XNS packets transmitted and received by the router, use the show xns traffic EXEC command.
show xns trafficThis command has no arguments or keywords.
EXEC
The following is sample output from the show xns traffic command:
Router# show xns traffic
Rec: 3968 total, 0 format errors, 0 checksum errors, 0 bad hop count,
3968 local destination, 0 multicast
Bcast: 2912 received, 925 sent
Sent: 5923 generated, 500 forwarded, 0 encapsulation failed, 0 not routable
Errors: 10 received, 20 sent
Echo: Recd: 100 requests, 89 replies Sent: 20 requests, 20 replies
Unknown: 5 packets
Table 21-6 describes significant fields shown in the display.
| Field | Description |
|---|---|
Rec: | Description of the XNS packets the router has received. |
3968 total | Total number of packets the router has received. |
0 format errors | Number of bad packets discarded (for example, packets with a corrupted header). |
0 checksum errors | Number of packets discarded because they contained checksum errors. |
0 bad hop count | Number of packets discarded because their hop count exceeded 16 (that is, the packets timed out). |
3968 local destination | Number of packets sent to the local broadcast address or specifically to the router. |
0 multicast | Number of packets received that were addressed to multiple destinations. |
Bcast: | Number of broadcast packets received and sent. |
Sent: | Description of the XNS packets the router has sent. |
5923 generated | Number of packets the router transmitted that it generated itself. |
500 forwarded | Number of packets the router transmitted that it forwarded from other sources. |
0 encapsulation failed | Number of packets the router was unable to encapsulate. |
0 not routable | Number of times the router could not locate in the routing table a route to the destination. |
Errors: | Number of packets the router sent and received that contained errors. |
Echo: | Number of ping packets the router received and sent, and the number of replies it received. |
Unknown: | Number of packets the router was unable to forward, for example, because of a misconfigured helper address or because no route was available. |
To apply a generic filter to an interface, use the xns access-group interface configuration command. To remove the access list, use the no form of this command.
xns access-group access-list-number
access-list-number | Number of the access list. All outgoing packets defined with either standard or extended access lists and forwarded through the interface are filtered by the entries in this access list. For standard access lists, access-list-number is a decimal number from 400 to 499. For extended access lists, access-list-number is a decimal number from 500 to 599. |
None
Interface configuration
The xns access-group command applies a generic filter to an interface. These filters control which packets are sent out an interface based on the packet's source and destination addresses, XNS protocol type, and source and destination socket numbers. You use the access-list (standard) and access-list (extended) commands to specify the filtering conditions.
You can apply only one filter to an interface.
In the following example, the access list 500 is applied to Ethernet interface 0.
interface ethernet 0
xns access-group 500
access-list (standard)
access-list (extended)
To select the type of encapsulation used on a Token Ring interface, use the xns encapsulation interface configuration command. To disable the encapsulation, use the no form of this command.
xns encapsulation {snap | ub | 3com}
snap | 802.2 LLC encapsulation. This is the default encapsulation type. Use this encapsulation type with IBM Token Ring networks. |
ub | Ungermann-Bass encapsulation. |
3com | 3Com encapsulation. Use this encapsulation type when older 3Com Corporation products are present on the network. |
snap
Interface configuration
You must specify this command on an interface if you want a Token Ring interface to forward XNS packets.
Some 3Com 3+ hosts do not recognize Token Ring packets with the source-route bridging RIF field set. You can work around this discrepancy by using the no multiring xns interface configuration command on Token Ring interfaces that are used for 3Com XNS routing. See the "Source-Route Bridging Commands" chapter for more information.
In the following example, Ungermann-Bass-style encapsulation is used when forwarding Token Ring packets across an interface:
interface tokenring 0
xns network 23
xns encapsulation ub
A dagger (†) indicates that the command is documented in another chapter.
multiring xns †
xns hear-rip
xns ub-emulation
To flood broadcast packets whose destination address is -1.FFFF.FFFF.FFFF, use the xns flood broadcast allnets interface configuration command. To disable this type of flooding, use the no form of this command.
xns flood broadcast allnetsThis command has no arguments or keywords.
Disabled
Interface configuration
The xns flood broadcast allnets command configures all-nets flooding. In this type of routing, all broadcast packets are sent to all networks (as indicated by the network address -1) and to all host on those networks (as indicated by the host address FFFF.FFFF.FFFF).
You can specify a network address of -1 only with the xns flood broadcast commands. In all other commands, it is an invalid address.
Flooding is applied to the packets received on an interface.
It is most closely in accordance with the XNS specification to flood packets with destinations of
-1.FFFF.FFFF.FFFF and destinations of -1.specific-host, but not to flood packets with destinations of 0.FFFF.FFFF.FFFF.
The following example configures the interface to flood broadcast packets:
interface ethernet 0
xns network 20
xns broadcast allnets
xns flood broadcast net-zero
xns hear-rip
To flood packets whose destinations address is 0.FFFF.FFFF.FFFF, use the xns flood broadcast net-zero interface configuration command. To disable this type of flooding, use the no form of this command.
xns flood broadcast net-zeroThis command has no arguments or keywords.
Disabled
Interface configuration
The xns flood broadcast net-zero command sends broadcast packets to all hosts (as indicated by the host address FFFF.FFFF.FFFF) on the local network (as indicated by the network address 0). This broadcast configuration is required in some 3Com environments.
Flooding is applied to the packets received on an interface.
In the following example, broadcast packets destined for the local network are sent to all hosts on that network:
interface Ethernet 0
xns network 20
xns flood broadcast net-zero
xns flood broadcast allnets
xns flood specific allnets
xns hear-rip
To flood packets whose destination address is -1.specific-host, use the xns flood specific allnets interface configuration command. To disable this type of flooding, use the no form of this command.
xns flood specific allnetsThis command has no arguments or keywords.
Disabled
Interface configuration
The xns flood specific allnets command forwards broadcast packets as MAC-layer broadcasts so that they can be picked up and further flooded by other routers.
You can specify a network address of -1 only with the xns flood broadcast commands. In all other commands, it is an invalid address.
Flooding is applied to the packets received on an interface.
It is most closely in accordance with the XNS specification to flood packets with destinations of
-1.FFFF.FFFF.FFFF and destinations of -1.specific-host, but not to flood packets with destinations of 0.FFFF.FFFF.FFFF.
In the following example, packets with destinations of -1.specific-host are flooded:
interface Ethernet 0
xns network 20
xns flood broadcast specific allnets
xns flood broadcast allnets
xns flood broadcast net-zero
xns hear-rip
To forward packets of a specific XNS protocol to a helper address, use the xns forward-protocol global configuration command. To disable the forwarding of these packets, use the no form of this command.
xns forward-protocol protocol
protocol | Number of an XNS protocol, in decimal. See the documentation accompanying your host's XNS implementation for a list of protocol numbers. |
Disabled
Global configuration
In the following example, packets of protocol type 2 are forwarded to the specified helper address:
xns forward-protocol 2
interface ethernet 0
xns helper-address 26.FFFF.FFFF.FFFF
To receive RIP updates, use the xns hear-rip interface configuration command. To disable the receipt of RIP updates, use the no form of this command.
xns hear-rip [access-list-number]
access-list-number | (Optional) Number of the access list. This list defines the routes the router is to learn through standard RIP. The list is applied to individual routes within the RIP packet, not to the address of the packet's sender. For standard access lists, access-list-number is a decimal number from 400 to 499. For extended access lists, access-list-number is a decimal number from 500 to 599. |
Disabled
Interface configuration
Delay metrics are computed as if each hop mentioned by the RIP update were a 9.6-kbps serial link. Ordinarily, the result is that our router prefers an all-Ungermann-Bass path over an all-RIP path. If you want the router to learn only certain routes through standard RIP, specify an access list number as an argument to the xns hear-rip command. The router will then learn from RIP packets only routes to networks permitted by the access list. Note that the access list is applied to individual routes within the RIP packet, not to the address of the packet's sender.
In an Ungermann-Bass environment, you should configure all interfaces with the xns flood broadcast allnets and xns flood specific allnets commands. You should not configure them with the xns flood broadcast net-zero command. You should configure Token Ring interfaces that are directly connected to Ungermann-Bass nodes with the xns encapsulation ub command.
In the following example, serial interface 0 receives RIP updates:
interface serial 0
xns network 24
xns hear-rip
xns encapsulation ub
xns flood broadcast allnets
xns flood broadcast net-zero
xns flood specific allnets
xns ub-emulation
To forward broadcast packets to a specified server, use the xns helper-address interface configuration command. To disable this function, use the no form of this command.
xns helper-address network.host
network | Network on which the target XNS server resides. This is a 32-bit decimal number. |
host | Host number of the target XNS server. This is a 48-bit hexadecimal value represented as a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). The host must be directly connected to one of the router's directly attached networks. A number of FFFF.FFFF.FFFF indicates all hosts on the specified network. |
Disabled
Interface configuration
Routers normally block all broadcast requests and do not forward them to other network segments. This is done to prevent the degradation of performance over the entire network. The xns helper-address command allows broadcasts to be forwarded to other networks. This is useful when a network segment does not have a server capable of handling broadcasts. This command lets you forward the broadcasts to a server, network, or networks that can process them. Incoming unrecognized broadcast packets that match the access list created with the xns helper-list command, if it is present, are forwarded.
When a packet is helpered, the router changes its destination address to be the configured helper address, and the packet is routed toward that address. The host at the helper address is expected to process the packet and (usually) to reply to the packet's sender. A helper address can be a directed broadcast address, in which case the helpered packet will be forwarded to a remote network and rebroadcast there.
You can specify multiple xns helper-address commands on a given interface.
In the following example, the server at address 0000.0c00.23fe receives all broadcasts on network 51:
xns helper-address 51.0000.0c00.23fe
To control which networks are added to the routing table, use the xns input-network-filter interface configuration command. To remove the filter from the interface, use the no form of this command.
xns input-network-filter access-list-number
access-list-number | Number of the access list. All incoming packets defined with either standard or extended access lists are filtered by the entries in this access list. For standard access lists, access-list-number is a decimal number from 400 to 499. For extended access lists, it is a decimal number from 500 to 599. |
None
Interface configuration
The xns input-network-filter command controls which networks are added to the routing table based on the networks learned in incoming XNS routing updates (RIP updates) on the interface.
You can issue only one xns input-network-filter command on each interface.
In the following example, access list 476 controls which networks are added to the routing table when RIP packets are received on Ethernet interface 1. Network 16 is the only network whose information will be added to the routing table. Routing updates for all other networks are implicitly denied and are not added to the routing table.
access-list 476 permit 16
interface ethernet 1
xns input-network-filter 476
access-list (standard)
access-list (extended)
xns output-network-filter
To set the maximum number of paths the router uses when sending packets, use the xns maximum-paths global configuration command. To restore the default value, use the no form of this command.
xns maximum-paths number
number | Maximum number of equal-cost paths from which the router chooses. It can be a number from 1 to 512. The default is 1. |
1 path
Global configuration
A router can use multiple paths to reach an XNS destination in order to increase throughput in the network. By default, the router will pick one best path and send all traffic on this path, but you can configure it to remember two or more paths that have equal costs (the cost metric is hop count for standard XNS RIP) and to balance the traffic load across all the available paths. (Note that when paths have differing costs, the router chooses lower-cost routes in preference to higher-cost routes.) Packets are distributed over the multiple paths in round-robin fashion on a packet-by-packet basis. That is, the first packet is sent along the first path, the second packet along the second path, and so on. If the final path is reached before all packets are sent, the next packet is sent to the first path, the next to the second path, and so on.
Limiting the number of equal-cost paths can save memory on routers with limited memory or very large configurations. Additionally, in networks with a large number of multiple paths and systems with limited ability to cache out-of-sequence packets, performance might suffer when traffic is split between many paths.
In the following example, the router uses up to two alternate paths:
xns maximum-paths 2
To enable XNS routing on a particular interface by assigning a network number to the interface, use the xns network interface configuration command. To disable XNS routing on an interface, use the no form of this command.
xns network number
number | Network number. This is a 32-bit decimal number. You can omit leading zeros. |
XNS routing disabled
Interface configuration
Interfaces not enabled to run XNS ignore any XNS packets that they receive.
Every XNS interface must have a unique XNS network number.
The following example enables XNS routing, specifying that XNS networks 20 and 21 are connected to two of the router's Ethernet interfaces:
xns routing
interface ethernet 0
xns network 20
interface ethernet 1
xns network 21
To control the list of networks included in routing updates sent out an interface, use the xns output-network-filter interface configuration command. To remove the filter from the interface, use the no form of this command.
xns output-network-filter access-list-number
access-list-number | Number of the access list. All outgoing packets defined with either standard or extended access lists are filtered by the entries in this access list. For standard access lists, access-list-number is a decimal number from 400 to 499. For extended access lists, it is a decimal number from 500 to 599. |
None
Interface configuration
The xns output-network-filter command controls which networks the router advertises in its routing updates (RIP updates).
You can issue only one xns output-network-filter command on each interface.
In the following example, access list 496 controls which networks are specified in routing updates sent out the serial 1 interface. This configuration causes network 27 to be the only network advertised in routing updates sent on the defined serial interface.
access-list 496 permit 27
interface serial 1
xns output-network-filter 496
xns input-network-filter
xns router-filter
To add a static route to the XNS routing table, use the xns route global configuration command. To remove a route from the routing table, use the no form of this command.
xns route network network.host
network | Network to which you want to establish a static route. This is a 32-bit decimal number. You can omit leading zeros. |
network.host | Router to which to forward packets destined for the specified network. The argument network is a 32-bit decimal number. You can omit leading zeros. The argument host is the host number of the target router. This is a 48-bit value represented by a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). |
None
Global configuration
The xns route command forwards packets destined for the specified network (network) to the specified router (network.host), regardless of whether that router is sending dynamic routing information.
Static routes usually are not used in XNS environments, because nearly all XNS routers support dynamic routing via RIP. Dynamic routing is enabled by default in our routers.
Be careful when assigning static routes. When links associated with static routes are lost, traffic may stop being forwarded, even though alternative paths might be available.
In the following example, the router at address 21.0456.acd3.1243 handles all traffic destined for network 25:
xns routing
xns route 25 21.0456.acd3.1243
To enable XNS fast switching, use the xns route-cache interface configuration command. To disable fast switching, use the no form of this command.
xns route-cacheThis command has no arguments or keywords.
Enabled
Interface configuration
XNS fast switching allows higher throughput by switching packets using a cache created by previous transit packets.
You might want to disable fast switching in two situations. One is if you want to save memory on the interface cards: fast-switching caches require more memory than those used for standard switching. The second situation is to avoid congestion on interface cards when a high-bandwidth interface is writing large amounts of information to a low-bandwidth interface.
In the following example, XNS fast switching is disabled for interface serial 1:
interface serial 1
no xns route-cache
To control the routers from which packets are accepted, use the xns router-filter interface configuration command. To remove the filters from the interface, use the no form of this command.
xns router-filter access-list-number
access-list-number | Number of the access list. All incoming packets defined with either standard or extended access lists are filtered by the entries in this access list. For standard access lists, access-list-number is a decimal number from 400 to 499. For extended access lists, it is a decimal number from 500 to 599. |
None
Interface configuration
You can issue only one xns router-filter command on each interface.
In the following example, access list 466 controls the routers from which packets are accepted. For serial interface 0, only packets from the router at 26.0000.00c0.047d are accepted. All other packets are implicitly denied.
access-list 466 permit 26.0000.00c0.047d
interface serial 0
xns router-filter 466
xns input-network-filter
xns output-network-filter
To enable XNS routing, use the xns routing global configuration command. To disable XNS routing, use the no form of this command.
xns routing [address]
address | (Optional) Host number of the router. This is a 48-bit value represented by a dotted triplet of four-digit hexadecimal numbers (xxxx.xxxx.xxxx). It must not be a multicast address. If you omit address, the router uses the address of the first IEEE-compliant (Token Ring, FDDI, or Ethernet) interface MAC address it finds in its interface list. The router uses the address 0123.4567.abcd for non-IEEE-compliant interfaces. |
Disabled
Global configuration
The xns routing command enables the RIP service on the router.
The following example enables XNS routing on the router:
xns routing
To enable Ungermann-Bass Net/One routing, use the xns ub-emulation global configuration command. To disable Net/One routing and restore standard routing mode, use the no form of this command.
xns ub-emulationThis command has no arguments or keywords.
Disabled
Global configuration
The xns ub-emulation command enables Ungermann-Bass Net/One routing. This means that Hello packets and routing updates on all XNS interfaces are sent out in Ungermann-Bass format.
Net/One is a distance-vector, or Bellman-Ford, protocol, similar to standard XNS RIP. The major difference between the two protocols is in the metrics used. Standard XNS RIP uses a hop count to determine the best route to distant networks and maintains information only about hop counts. The Ungermann-Bass protocol uses a path-delay metric and maintains information about both hop counts and its own metrics.
Ungermann-Bass routers generate standard RIP updates by extracting the hop-count values from the Ungermann-Bass routing protocol. When configured in Ungermann-Bass emulation mode, routers participate in this protocol and behave (insofar as routing protocols are concerned) like Ungermann-Bass routers.
You can use the xns hear-rip command to configure routers to listen to standard RIP updates when in Ungermann-Bass emulation mode. When our router in Ungermann-Bass emulation mode receives a RIP packet, each route in that packet is treated as though it had come from an Ungermann-Bass routing packet. The hop count used is the actual hop count from the RIP packet. The delay metric used is computed by assuming that each hop is the longest-delay link used by Ungermann-Bass, which is a 9.6-kbps serial link. Information from RIP packets is used in creating outgoing Ungermann-Bass updates, and vice versa.
To enable Ungermann-Bass routing on routers running Software Release 8.3 or earlier, use the xns ub-routing global configuration command. This command has been retained for backward compatibility with earlier software releases. To disable Ungermann-Bass routing, use the no form of this command.
xns ub-routingThis command is never written to nonvolatile configuration memory. Instead, the equivalent individual commands are written.These are an xns ub-emulation command for the router, and xns hear-rip, xns flood broadcast allnets, no xns flood broadcast net-zero, and xns flood specific allnets commands for all interfaces on which XNS is enabled. The xns ub-routing command does not modify the encapsulation used on Token Ring interfaces.
Older versions of our software implemented a restricted version of the Ungermann-Bass routing protocol, and in certain configurations could create routing instability and forwarding loops. Before using Software Releases 8.3 and earlier in Ungermann-Bass environments, consult the 8.3 documentation for information about these restrictions.
The following example enables Net/One routing:
xns routing
xns ub-emulation
interface tokenring 0
xns network 23
xns encapsulation ub
xns encapsulation ub
xns hear-rip
To set the XNS routing update timers, use the xns update-time interface configuration command. To restore the default value, use the no form of this command.
xns update-time interval
interval | Interval, in seconds, at which XNS routing updates are sent. The minimum interval is 10 seconds, and the maximum is 2,493,644 seconds, which is about 29 days. The default is 30 seconds. |
30 seconds
Interface configuration
The xns update-time command sets the routing update timer on a per-interface basis. To display the current value, use the show xns routecommand.
Routers exchange information about routes by sending broadcast messages when they are brought up and shut down, and periodically while they are running. The xns update-time command lets you modify the periodic update interval.
You can set RIP timers only in a configuration in which all routers are our routers. The timers should be the same for all routers connected to the network.
The update value you choose affects the internal XNS timers as follows:
This command has no effect on the Ungermann-Bass routing protocol.
The following example sets the routing update time to 20 seconds:
interface ethernet 0
xns network 20
xns update-time 20
Posted: Mon Oct 21 11:18:44 PDT 2002
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