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Use the commands in this chapter to configure and monitor transparent bridging networks. For transparent bridging configuration information and examples, refer to the "Configuring Transparent Bridging" chapter in the Router Products Configuration Guide.
Use the access-list global configuration command to establish MAC address access lists. Use the no form to remove a single access list entry.
access-list access-list-number {permit | deny} address mask| access-list-number | Integer from 700 to 799 that you select for the list. |
| permit | Permits the frame. |
| deny | Denies the frame. |
| address mask | 48-bit MAC addresses written in dotted triplet form. The ones bits in the mask argument are the bits to be ignored in address. |
No MAC address access lists are established.
Global configuration
This following example assumes that you want to disallow the bridging of Ethernet packets of all Sun workstations on Ethernet 1. Software assumes that all such hosts have Ethernet addresses with the vendor code 0800.2000.0000. The first line of the access list denies access to all Sun workstations, while the second line permits everything else. You then assign the access list to the input side of Ethernet 1.
access-list 700 deny 0800.2000.0000 0000.00FF.FFFF
access-list 700 permit 0000.0000.0000 FFFF.FFFF.FFFF
interface ethernet 1
bridge-group 1 input-address-list 700
access-list (extended)
access-list (type-code)
Use the access-list global configuration command to provide extended access lists that allow finer granularity of control. These lists allow you to specify both source and destination addresses and arbitrary bytes in the packet.
access-list access-list-number {permit | deny} source source-mask destination| access-list-number | Integer from 1100 through 1199 that you assign to identify one or more permit/deny conditions as an extended access list. Note that a list number in the range 1100 through 1199 distinguishes an extended access list from other access lists. |
| permit | Allows a connection when a packet matches an access condition. The router stops checking the extended access list after a match occurs. All conditions must be met to make a match. |
| deny | Disallows a connection when a packet matches an access condition. The router stops checking the extended access list after a match occurs. All conditions must be met to make a match. |
| source | MAC Ethernet address in the form xxxx.xxxx.xxxx. |
| source-mask | Mask of MAC Ethernet source address bits to be ignored. The router uses the source and source-mask arguments to match the source address of a packet. |
| destination | MAC Ethernet value used for matching the destination address of a packet. |
| destination-mask | Mask of MAC Ethernet destination address bits to be ignored. The router uses the destination and destination mask arguments to match the destination address of a packet. |
| offset | Range of values that must be satisfied in the access list. Specified in decimal or in hexadecimal format in the form 0xnn. The offset is the number of bytes from the destination address field; it is not an offset from the start of the packet. The number of bytes you need to offset from the destination address varies depending on the media encapsulation type you are using. |
| size | Range of values that must be satisfied in the access list. Must be an integer 1 through 4. |
| operator | Compares arbitrary bytes within the packet. Can be one of the following keywords:
lt--less than gt--greater than eq--equal neq--not equal and--bitwise and xor--bitwise exclusive or nop--address match only |
| operand | Compares arbitrary bytes within the packet. The value to be compared to or masked against. |
No extended access lists are established.
Global configuration
After an access list is initially created, any subsequent additions (possibly entered from the terminal) are placed at the end of the list. In other words, you cannot selectively add or remove access list command lines from a specific access list.
An extended access list should not be used on FDDI interfaces that provide transit bridging.
 | Caution Do not specify offsets into a packet that are greater than the size of the packet. |
The following example permits packets from MAC addresses 000c.1Bxx.xxxx to any MAC address if the packet contains a value less than 0x55AA in the 2 bytes that begins 0x1E bytes into the packet:
interface ethernet 0
bridge-group 3 output-pattern 1102
access-list 1102 permit 000c.1b00.0000 0000.00ff.ffff
0000.0000.0000 ffff.ffff.ffff 0x1e 2 lt 0x55aa
The following example permits a NOP operation:
interface ethernet 0
bridge-group 3 output-pattern 1102
access-list 1101 permit 0000.0000.0000 ffff.ffff.ffff 0000.0000.0000 ffff.ffff.ffff
access-list (standard)
access-list (type-code)
bridge-group output-pattern
Use the access-list global configuration command to build type-code access lists. Use the no form of the command to remove a single access list entry.
access-list access-list-number {permit | deny} type-code wild-mask| access-list-number | User-selectable number between 200 and 299 that identifies the list. |
| permit | Permits the frame. |
| deny | Denies the frame. |
| type-code | 16-bit hexadecimal number written with a leading "0x"; for example, 0x6000. You can specify either an Ethernet type code for Ethernet-encapsulated packets, or a DSAP/SSAP pair for 802.3 or 802.5-encapsulated packets. Ethernet type codes are listed in the appendix "Ethernet Type Codes." |
| wild-mask | 16-bit hexadecimal number whose ones bits correspond to bits in the type-code argument that should be ignored when making a comparison. (A mask for a DSAP/SSAP pair should always be at least 0x0101. This is because these two bits are used for purposes other than identifying the SAP codes.) |
No type-code access lists are built.
Global configuration
Type-code access lists can have an impact on system performance; therefore, keep the lists as short as possible and use wildcard bit masks whenever possible.
Access lists are evaluated according to the following algorithm:
If the length/type field is greater than 1500, the packet is treated as an LSAP packet unless the DSAP and SSAP fields are AAAA. If the latter is true, the packet is treated using type-code filtering.
If the LSAP-code filtering is used, all SNAP and Ethernet Type II packets are bridged without obstruction. If type-code filtering is used, all LSAP packets are bridged without obstruction.
If you have both Ethernet Type II and LSAP packets on your network, you should set up access lists for both.
The following example permits only LAT frames (type 0x6004) and filters out all other frame types:
access-list 201 permit 0x6004 0x0000
The following example filters out only type codes assigned to DEC (0x6000 through 0x600F) and lets all other types pass:
access-list 202 deny 0x6000 0x600F
access-list 202 permit 0x0000 0xFFFF
Use the last item of an access list to specify a default action; for example, permit everything else or deny everything else. If nothing else in the access list matches, the default action is normally to deny access; that is, filter out all other type codes.
access-list (standard)
access-list (extended)
Use the bridge acquire global configuration command to use the system default behavior of forwarding any frames for stations that it has learned about dynamically. Use the no bridge acquire global configuration command to change the default behavior.
bridge bridge-group acquire| bridge-group | Bridge group number. Must be the same as that specified in the bridge protocol command. |
Enabled
Global configuration
When using the command default, the router forwards any frames from stations that its has learned about dynamically. If you use the no form of this command, the bridge stops forwarding frames to stations it has dynamically learned about through the discovery process and limits frame forwarding to statically configured stations. That is, the bridge filters out all frames except those whose sourced-by or destined-to addresses have been statically configured into the forwarding cache. The no form of this command prevents the forwarding of a dynamically learned address.
The following example prevents the forwarding of dynamically determined source and destination addresses:
no bridge 1 acquire
bridge address
Use the bridge address global configuration command to filter frames with a particular MAC layer station source or destination address. Use the no bridge address command followed by the MAC address to disable the forwarding ability.
bridge bridge-group address mac-address {forward | discard} [interface]| bridge-group | Group number you assigned to the spanning tree. Must be the same as that specified in the bridge protocol command. |
| mac-address | 48-bit dotted-triplet hardware address such as that displayed by the EXEC show arp command, for example, 0800.cb00.45e9. It is either a station address, the broadcast address, or a multicast destination address. |
| forward | Frame sent from or destined to the specified address is forwarded as appropriate. |
| discard | Frame sent from or destined to the specified address is discarded without further processing. |
| interface | (Optional) Interface specification, such as Ethernet 0. It is added after the forward or discard keyword to indicate the interface on which that address can be reached. |
Disabled
Global configuration
Any number of addresses can be configured into the system without a performance penalty.
The following example enables frame filtering with MAC address 0800.cb00.45e9. The frame is forwarded through interface Ethernet 1:
bridge 1 address 0800.cb00.45e9 forward ethernet 1
The following example disables the ability to forward frames with MAC address 0800.cb00.45e9:
no bridge 1 address 0800.cb00.45e9
bridge acquire
bridge-group input-address-list
bridge-group output-address-list
Use the bridge circuit-group pause global configuration command to configure the interval during which transmission is suspended in a circuit group after circuit group changes take place.
bridge bridge-group circuit-group circuit-group pause milliseconds| bridge-group | Number of the bridge group to which the interface belongs. |
| circuit-group | Number of the circuit group to which the interface belongs. |
| milliseconds | Forward delay interval. It must be a value in the range 0 through 10000 milliseconds. |
0 millisecond pause
Global configuration
Circuit-group changes include the addition or deletion of an interface, and interface state changes.
The following example sets the circuit group pause to 5000 milliseconds:
bridge 1 circuit-group 1 pause 5000
bridge circuit-group source-based
bridge-group circuit-group
show bridge circuit-group
Use the bridge circuit-group source-based global configuration command to use just the source MAC address for selecting the output interface. Use the no form of this command to remove the interface from the bridge group.
bridge bridge-group circuit-group circuit-group source-based| bridge-group | Number of the bridge group to which the interface belongs |
| circuit-group | Number of the circuit group to which the interface belongs |
No bridge group interface is assigned
Global configuration
For applications that depend on the ordering of mixed unicast and multicast traffic from a given source, load distribution must be based on the source MAC address only. The bridge circuit-group source-based command modifies the load distribution strategy to accommodate such applications.
The following example uses the source MAC address for selecting the output interface to a bridge group:
bridge 1 circuit-group 1 source-based
bridge circuit-group pause
bridge-group circuit-group
show bridge circuit-group
Use the bridge domain global configuration command to establish a domain by assigning it a decimal value between 1 and 10. Use the no form of the command to return it to a single bridge domain by choosing domain zero (0).
bridge bridge-group domain domain-number| bridge-group | Bridge group number. It must be the same as that specified in the bridge protocol ieee command. The dec keyword is not valid for this command. |
| domain-number | Domain number you choose. The default domain number is zero; this is the domain number required when communicating to IEEE bridges that do not support this domain extension. |
Single bridge domain
Global configuration
Cisco has implemented a proprietary extension to the IEEE spanning-tree software in order to support multiple spanning-tree domains. You can place any number of router/bridges within the domain. The devices in the domain, and only those devices, will then share spanning-tree information.
Use this feature when multiple routers share the same cable, and you wish to use only certain discrete subsets of those routers to share spanning-tree information with each other. This function is most useful when running other router applications, such as IP UDP flooding, that use the IEEE spanning tree. It also can be used to reduce the number of global reconfigurations in large bridged networks.
| Caution Use multiple spanning-tree domains with care. Because bridges in different domains do not share spanning-tree information, bridge loops can be created if the domains are not carefully planned. |
The following example places bridge group 1 in bridging domain 3. Only other routers that are in domain 3 will accept spanning-tree information from this router.
bridge 1 domain 3
bridge protocol
bridge-group
Use the bridge forward-time global configuration command to specify the forward delay interval for the router. Use the no form of this command to return the default interval.
bridge bridge-group forward-time seconds| bridge-group | Bridge group number. It must be the same as specified in the bridge protocol command. |
| seconds | Forward delay interval. It must be a value in the range 10 through 200 seconds. |
30 seconds
Global configuration
The forward delay interval is the amount of time the router spends listening for topology change information after an interface has been activated for bridging and before forwarding actually begins.
Each bridge in a spanning tree adopts the hello-time, forward-time, and max-age parameters of the root bridge, regardless of what its individual configuration might be.
The following example sets the forward delay interval to 60 seconds:
bridge 1 forward-time 60
bridge hello-time
bridge max-age
Use the bridge hello-time global configuration command to specify the interval between Hello Bridge Protocol Data Units (BPDUs). Use the no form of this command to return the default interval.
bridge bridge-group hello-time seconds| bridge-group | Bridge group number. It must be the same as specified in the bridge protocol command. |
| seconds | Any value between 1 and 10 seconds. |
1 second
Global configuration
Each bridge in a spanning tree adopts the hello-time, forward-time, and max-age parameters of the root bridge, regardless of what its individual configuration might be.
The following example sets the interval to 5 seconds:
bridge 1 hello-time 5
bridge forward-time
bridge max-age
Use the bridge lat-service-filtering global configuration command to specify LAT group-code filtering. Use the no form of the command to disable the use of LAT service filtering on the bridge group.
bridge bridge-group lat-service-filtering| bridge-group | Bridge group in which this special processing is to take place |
LAT service filtering is disabled.
Global configuration
This command informs the system that LAT service advertisements require special processing.
The following example specifies that LAT service announcements traveling across bridge group 1 require some special processing:
bridge 1 lat-service-filtering
Use the bridge max-age global configuration command to change the interval the bridge will wait to hear BPDUs from the root bridge. If a bridge does not hear BPDUs from the root bridge within this specified interval, it assumes that the network has changed and will recompute the spanning-tree topology. Use the no form of this command to return the default interval.
bridge bridge-group max-age seconds| bridge-group | Bridge group number. It must be the same as specified in the bridge protocol command. |
| seconds | Interval the bridge will wait to hear BPDUs from the root bridge. It must be a value in the range 10 through 200 seconds. |
15 seconds
Global configuration
Each bridge in a spanning tree adopts the hello-time, forward-time, and max-age parameters of the root bridge, regardless of what its individual configuration might be.
The following example increases the maximum idle interval to 20 seconds:
bridge 1 max-age 20
bridge forward-time
bridge hello-time
Use the bridge multicast-source global configuration command to configure bridging support to allow the forwarding, but not the learning, of frames received with multicast source addresses. Use the no form of this command to disable this function on the bridge.
bridge bridge-group multicast-source| bridge-group | Bridge group number. It must be the same as specified in the bridge protocol command. |
Disabled
Global configuration
If you need to bridge Token Ring over other medium, RSRB is recommended.
The following example allows the forwarding, but not the learning, of frames received with multicast source addresses:
bridge 2 multicast-source
Use the bridge priority global configuration command to configure the priority of an individual bridge, or the likelihood that it will be selected as the root bridge.
bridge bridge-group priority number| bridge-group | The bridge group number. It must be the same as specified in the bridge protocol command. |
| number | The lower the number, the more likely the bridge will be chosen as root. When the IEEE spanning-tree protocol is enabled on the router, number ranges from 0 through 65535. When the DEC spanning-tree protocol is enabled, number ranges from 0 through 255. |
When the IEEE spanning-tree protocol is enabled on the router: 32768
When the DEC spanning-tree protocol is enabled on the router: 128
Global configuration
When two bridges tie for position as the root bridge, an interface priority determines which bridge will serve as the root bridge. Use the bridge-group priority interface configuration command to control an interface priority.
The following example establishes this bridge as a likely candidate to be the root bridge:
bridge 1 priority 100
bridge-group priority
Use the bridge protocol global configuration command to define the type of spanning-tree protocol. Use the no bridge protocol command, with the appropriate keywords and arguments, to delete the bridge group.
bridge bridge-group protocol {ieee | dec}No spanning-tree protocol is defined.
Global configuration
The router/bridges support two spanning-tree protocols: the IEEE 802.1 standard and the earlier DEC spanning-tree protocol upon which the IEEE standard is based. Multiple domains are supported for the IEEE spanning tree.
The following example shows bridge 1 as using the DECnet spanning-tree protocol:
bridge 1 protocol dec
bridge domain
bridge-group
Use the bridge-group interface configuration command to assign each network interface to a bridge group. Use the no form of this command to remove the interface from the bridge group.
bridge-group bridge-group| bridge-group | Number of the bridge group to which the interface belongs. |
No bridge group interface is assigned.
Interface configuration
You can bridge on any interface, including any serial interface, regardless of encapsulation. Bridging can be configured between interfaces on different cards, although the performance is lower compared with interfaces on the same card. Also note that serial interfaces must be running with HDLC, X.25, or Frame Relay encapsulation.
In the following example, the Ethernet 0 interface is assigned to bridge-group 1, and bridging is enabled on this interface:
interface ethernet0
bridge-group 1
bridge protocol
bridge-group cbus-bridging
bridge-group circuit
bridge-group input-pattern
bridge-group output-pattern
bridge-group spanning-disabled
Use the bridge-group aging-time global configuration command to set the length of time that a dynamic entry can remain in the bridge table, from the time the entry was created or last updated. Use the no form of this command to return to the default aging-time interval.
bridge-group bridge-group aging-time seconds| bridge-group | Number of the bridge group to which the interface belongs. |
| seconds | Aging-time, in the range 0 through 1000000 seconds. The default is 300 seconds. |
300 seconds
Global configuration
If hosts on a bridged network are likely to move, decrease the aging-time to enable the bridge to adapt quickly to the change. If hosts do not transmit continuously, increase the aging-time to record the dynamic entries for a longer time and thus reduce the possibility of flooding when the hosts transmit again.
The following example sets the aging-time to 200 seconds:
bridge-group 1 aging-time 200
bridge-group
Use the bridge-group cbus-bridging interface configuration command to enable autonomous bridging on a ciscoBus II-resident interface. Use the no form of this command to disable autonomous bridging.
bridge-group bridge-group cbus-bridging| bridge-group | Number of the bridge group to which the interface belongs |
Autonomous bridging is disabled.
Interface configuration
Normally, bridging takes place on the processor card at interrupt level. When autonomous bridging is enabled, bridging takes place entirely on the ciscoBus II, significantly improving performance.
You can enable autonomous bridging on Ethernet, FDDI (FCIT) and HSSI interfaces that reside on a ciscoBus II. Autonomous bridging is not supported on Token Ring interfaces, regardless of the type of bus in use.
To enable autonomous bridging on an interface, that interface must first be defined as part of a bridge group. When a bridge group includes both autonomously and normally bridged interfaces, packets are autonomously bridged in some cases, but bridged normally in others. For example, when packets are forwarded between two autonomously bridged interfaces, those packets are autonomously bridged. But when packets are forwarded between an autonomously bridged interface and one that is not, the packet must be normally bridged. When a packet is flooded, the packet is autonomously bridged on autonomously bridged interfaces, but must be normally bridged on any others.
In the following example, autonomous bridging is enabled on the Ethernet 0 interface:
!
interface ethernet 0
bridge-group 1
bridge-group 1 cbus-bridging
!
bridge-group
Use the bridge-group circuit-group interface configuration command to assign each network interface to a bridge group. Use the no form of this command to remove the interface from the bridge group.
bridge-group bridge-group circuit-group circuit-group| bridge-group | Number of the bridge group to which the interface belongs. |
| circuit-group | Circuit group number. The range is 1 through 9. |
No bridge group interface is assigned
Interface configuration
Circuit groups are primarily intended for use with HDLC-encapsulated serial interfaces. They are not supported for packet-switched networks such as X.25 or Frame Relay. Circuit groups are best applied to groups of serial lines of equal bandwidth, but can accommodate mixed bandwidths as well.
In the following example, the Ethernet 0 interface is assigned to circuit group 1 of bridge group 1:
interface ethernet 0
bridge-group 1 circuit-group 1
bridge circuit-group pause
bridge circuit-group source-based
show bridge circuit-group
Use the bridge-group input-address-list interface configuration command to assign an access list to a particular interface. This access list is used to filter packets received on that interface based on their MAC source addresses. Use the no form of this command to remove an access list from an interface.
bridge-group bridge-group input-address-list| bridge-group | Bridge group number. It must be in the range 1 through 9 and the same as defined by the bridge-group command. |
| access-list-number | Access list number you assigned with the bridge access-list command. It must be in the range 700 through 799. |
No access list is assigned.
Interface configuration
The following example assumes you want to disallow the bridging of Ethernet packets of all Sun workstations on Ethernet 1. Software assumes that all such hosts have Ethernet addresses with the vendor code 0800.2000.0000. The first line of the access list denies access to all Sun workstations, while the second line permits everything else. You then assign the access list to the input side of Ethernet 1.
access-list 700 deny 0800.2000.0000 0000.00FF.FFFF
access-list 700 permit 0000.0000.0000 FFFF.FFFF.FFFF
interface ethernet 1
bridge-group 1 input-address-list 700
access-list
bridge address
bridge-group output-address-list
Use the bridge-group input-lat-service-deny interface configuration command to specify the group codes by which to deny access upon input. Use the no form of this command to remove this access condition.
bridge-group bridge-group input-lat-service-deny group-listNo group codes are specified.
Interface configuration
Autonomous bridging must be disabled to use this command.
This command causes the system to not bridge any LAT service advertisement that has any of the specified groups set.
The following example causes any advertisements with groups 6, 8, and 14 through 20 to be dropped:
interface ethernet 0
bridge-group 1 input-lat-service-deny 6 8 14-20
bridge-group input-lat-service-permit
bridge-group output-lat-service-deny
Use the bridge-group input-lat-service-permit interface configuration command to specify the group codes by which to permit access upon input. Use the no form of this command to remove this access condition.
bridge-group bridge-group input-lat-service-permit group-listNo group codes are specified.
Interface configuration
Autonomous bridging must be disabled to use this command.
This command causes the system to bridge only those service advertisements that match at least one group in the group list specified by the group-list argument.
If a message specifies group codes in both the deny and permit list, the message is not bridged.
The following example bridges any advertisements from groups 1, 5, and 12 through 14:
interface ethernet 1
bridge-group 1 input-lat-service-permit 1 5 12-14
bridge-group output-lat-service-permit
bridge-group input-lat-service-deny
Use the bridge-group input-lsap-list interface configuration command to filter IEEE 802.2-encapsulated packets on input. Use the no form of this command to disable this capability.
bridge-group bridge-group input-lsap-list access-list-number| bridge-group | Bridge group number. It must be the same as defined in the bridge-group command. It must be a value in the range 1 through 9. |
| access-list-number | Access list number you assigned with the bridge access-list command. Specify a zero (0) to disable the application of the access list on the bridge group. |
Disabled
Interface configuration
Autonomous bridging must be disabled to use this command.
This access list is applied to all IEEE 802.2 frames received on that interface prior to the bridge-learning process. SNAP frames also must pass any applicable Ethernet type-code access list.
The following example specifies access list 203 on interface Ethernet 1:
interface ethernet 1
bridge-group 3 input-lsap-list 203
access-list
bridge-group output-lsap-list
Use the bridge-group input-pattern interface configuration command to associate an extended access list with a particular interface in a particular bridge group. Use the no form of this command to disable this capability.
bridge-group bridge-group input-pattern access-list-number| bridge-group | The bridge group number. It must be the same as defined in the bridge-group command. It must be a value in the range 1 through 9. |
| access-list-number | Access list number you assigned using the bridge access-list command. Specify a zero (0) to disable the application of the access list on the interface. |
Disabled
Interface configuration
Autonomous bridging must be disabled to use this command.
The following command applies access list 1 to bridge group 3 using the filter defined in group 1:
interface Ethernet 0
bridge-group 3 input-pattern 1
access-list
bridge-group
bridge-group output-pattern
Use the bridge-group input-type-list interface configuration command to filter Ethernet- and SNAP-encapsulated packets on input. Use the no form of this command to disable this capability.
bridge-group bridge-group input-type-list access-list-number| bridge-group | Bridge group number. It must be the same as defined in the bridge-group command. |
| access-list-number | Access list number you assigned with the bridge access-list command. Specify a zero (0) to disable the application of the access list on the bridge group. |
Disabled
Interface configuration
Autonomous bridging must be disabled to use this command.
For SNAP-encapsulated frames, the access list is applied against the 2-byte TYPE field given after the DSAP/SSAP/OUI fields in the frame.
This access list is applied to all Ethernet and SNAP frames received on that interface prior to the bridge learning process. SNAP frames also must pass any applicable IEEE 802 DSAP/SSAP access lists.
The following example shows how to configure a Token Ring interface with an access list that allows only the LAT protocol to be bridged:
interface tokenring 0
ip address 131.108.1.1 255.255.255.0
bridge-group 1
bridge-group 1 input-type-list 201
access-list
bridge-group output-type-list
Use the bridge-group lat-compression interface configuration command to reduce the amount of bandwidth that LAT traffic consumes on the serial interface by specifying a LAT-specific form of compression. Use the no form of this command to disable LAT compression on the bridge group.
bridge-group bridge-group lat-compression| bridge-group | Bridge group number. It must be the same as defined in the bridge-group command. |
Disabled
Interface configuration
Autonomous bridging must be disabled to use this command.
Compression is applied to LAT frames being sent out the router/bridge through the interface in question.
LAT compression can be specified only for serial interfaces. For the most common LAT operations (user keystrokes and acknowledgment packets), LAT compression reduces LAT's bandwidth requirements by nearly a factor of two.
The following example compresses LAT frames on the bridge assigned to group 1:
bridge-group 1 lat-compression
Use the bridge-group output-address-list interface configuration command to assign an access list to a particular interface for filtering the MAC destination addresses of packets that would ordinarily be forwarded out that interface. Use the no form of this command to remove an access list from an interface.
bridge-group bridge-group output-address-list access-list-number| bridge-group | Bridge group number in the range 1 through 9. It must be the same as defined in the bridge-group command. |
| access-list-number | Access list number you assigned with the bridge access-list command. |
No access list is assigned.
Interface configuration
The following example assigns access list 703 to interface Ethernet 3:
interface ethernet 3
bridge-group 5 output-address-list 703
access-list
bridge address
bridge-group input-address-list
Use the bridge-group output-lat-service-deny interface configuration command to specify the group codes by which to deny access upon output. Use the no form of this command to cancel the specified group codes.
bridge-group bridge-group output-lat-service-deny group-list| bridge-group | Bridge group number in the range 1 through 9. It must be the same as specified in the bridge-group command. |
| group-list | List of LAT groups. Single numbers and ranges are permitted. |
No group codes are assigned.
Interface configuration
Autonomous bridging must be disabled to use this command.
This command causes the system to not bridge onto this output interface any service advertisements that contain groups matching any of those in the group list.
The following example prevents bridging of LAT service announcements from groups 12 through 20:
interface ethernet 0
bridge-group 1
bridge-group 1 output-lat-service-deny 12-20
access-list
bridge-group input-lat-service-deny
bridge-group output-lat-service-permit
Use the bridge-group output-lat-service-permit interface configuration command to specify the group codes by which to permit access upon output. Use the no form of this command to cancel specified group codes.
bridge-group bridge-group output-lat-service-permit group-list| bridge-group | Bridge group number in the range 1 through 9. It must be the same as specified in the bridge-group command. |
| group-list | LAT service advertisements. |
No group codes are specified.
Interface configuration
Autonomous bridging must be disabled to use this command.
This command causes the system to bridge onto this output interface only those service
advertisements that match at least one group in the specified group code list.
The following example allows only LAT service announcements from groups 5, 12, and 20 on this bridge:
interface ethernet 0
bridge-group 1 output-lat-service-permit 5 12 20
bridge-group input-lat-service-permit
bridge-group output-lat-service deny
Use the bridge-group output-lsap-list interface configuration command to filter IEEE 802-encapsulated packets on output. Use the no form of this command to disable this capability.
bridge-group bridge-group output-lsap-list access-list-number| bridge-group | Bridge group number in the range 1 through 9. It must be the same as specified in the bridge-group command. |
| access-list-number | Access list number you assigned with the bridge access-list command. Specify a zero (0) to disable the application of the access list on the bridge group. |
Disabled
Interface configuration
Autonomous bridging must be disabled to use this command.
SNAP frames also must pass any applicable Ethernet type-code access list. This access list is applied just before sending out a frame to an interface.
For performance reasons, it is not a good idea to have both input and output type code filtering on the same interface.
Access lists for Ethernet- and IEEE 802-encapsulated packets affect only bridging functions. It is not possible to use such access lists to block frames with protocols that are being routed.
The following example specifies access list 204 on interface Ethernet 0:
interface ethernet 0
bridge-group 4 output-lsap-list 204
access-list
bridge-group input-lsap-list
Use the bridge-group output-pattern-list interface configuration command to associate an extended access list with a particular interface. Use the no form of this command to disable this capability.
bridge-group bridge-group output-pattern-list access-list-number| bridge-group | Bridge group number in the range 1 through 9. It must be the same as specified in the bridge-group command. |
| access-list-number | Extended access list number you assigned using the extended access-list command. Specify a zero (0) to disable the application of the access list on the interface. |
Disabled
Interface configuration
Autonomous bridging must be disabled to use this command.
The following example filters all packets sent by bridge group 3 using the filter defined in access list 1102.
interface Ethernet 0
bridge-group 3 output-pattern-list 1102
access-list (extended)
bridge-group
bridge-group input-pattern
Use the bridge-group output-type-list interface configuration command to filter Ethernet- and SNAP-encapsulated packets on output. Use the no form of this command to disable this capability.
bridge-group bridge-group output-type-list access-list-number| bridge-group | Bridge group number in the range 1 through 9. It must be the same as specified in the bridge-group command. |
| access-list-number | Access list number you assigned with the bridge access-list command. Specify a zero (0) to disable the application of the access list on the bridge group. This access list is applied just before sending out a frame to an interface. |
Disabled
Interface configuration
Autonomous bridging must be disabled to use this command.
The following example specifies access list 202 on interface Ethernet 0:
interface ethernet 0
bridge-group 2 output-type-list 202
access-list
bridge-group input-type-list
Use the bridge-group path-cost interface configuration command to set a different path cost. Use the no form of this command to choose the default path cost for the interface.
bridge-group bridge-group path-cost cost| bridge-group | Bridge group number. It must be the same as specified in the bridge-group command. |
| cost | Path cost can range from 1 through 65535, with higher values indicating higher costs. This range applies regardless of whether the IEEE or DEC spanning tree protocol has been specified. |
The default path cost is computed from the interface's bandwidth setting. The following are IEEE default path cost values. The DEC path cost default values are different.
Ethernet--100
16-Mb Token Ring--62
FDDI--10
HSSI--647
MCI/SCI Serial--647
Interface configuration
By convention, the path cost is 10000/data rate of the attached LAN (IEEE), or 100000/data rate of the attached LAN (DEC), in Mbps.
The following example changes the default path cost for interface Ethernet 0:
interface ethernet 0
bridge-group 1 path-cost 250
Use the bridge-group priority interface configuration command to set an interface priority when two bridges tie for position as the root bridge. The priority you set breaks the tie.
bridge-group bridge-group priority number| bridge-group | Bridge group number. It must be the same as specified in the bridge-group command. |
| number | Priority number ranging from 0 through 255 (DEC), or 0 through 64000 (IEEE). |
128--DEC spanning tree protocol
32768--IEEE spanning tree protocol
Interface configuration
The lower the number, the more likely it is that the bridge on the interface will be chosen as the root.
The following example increases the likelihood that the root bridge will be the one on Ethernet 0 in bridge group 1:
interface ethernet 0
bridge-group 1 priority 0
bridge priority
Use the bridge-group spanning-disabled interface configuration command to disable the spanning tree on a given interface.
bridge-group bridge-group spanning-disabled| bridge-group | Bridge group number of the interface. It must be the same as specified in the bridge-group command. |
Spanning tree enabled
Interface configuration
To enable transparent bridging on an interface, use the bridge protocol command to specify the type of spanning tree protocol to be used. The bridge-group spanning-disabled command can be used to disable that spanning tree on that interface.
When a loop-free path exists between any two bridged subnetworks, you can prevent BPDUs generated in one transparent bridging subnetwork from impacting nodes in the other transparent bridging subnetwork, yet still permit bridging throughout the bridged network as a whole.
For example, when transparently bridged LAN subnetworks are separated by a WAN, you can use this command to prevent BPDUs from traveling across the WAN link. You would apply this command to the serial interfaces connecting to the WAN in order to prevent BPDUs generated in one domain from impacting nodes in the remote domain. Because these BPDUs are prevented from traveling across the WAN link, using this command also has the secondary advantage of reducing traffic across the WAN link.
In the following example, the spanning tree for the serial 0 interface is disabled.
interface serial 0
bridge-group 1 spanning-disabled
bridge-group
bridge protocol
Use the bridge-group sse interface configuration command to enable Cisco's silicon switching engine (SSE) switching function. Use the no form of this command to disable SSE switching.
bridge-group bridge-group sse| bridge-group | Bridge group number. It must be a value in the range 1 through 9. |
Disabled
Interface configuration
The following example enables SSE switching:
bridge-group 1 sse
source-bridge
Use the clear bridge privileged EXEC command to remove any learned entries from the forwarding database and to clear the transmit and receive counts for any statically or system configured entries.
clear bridge bridge-group| bridge-group | Bridge group number. It must be a value in the range 1 through 9. |
Privileged EXEC
The following example shows the use of the clear bridge command:
clear bridge 1
bridge address
Use the clear sse privileged EXEC command to reinitialize the Silicon Switch Processor (SSP) on the Cisco 7000 series.
clear sseThis command has no arguments or keywords.
Disabled
Privileged EXEC
The silicon switching engine (SSE) is on the SSP board in the Cisco 7000.
The following example causes the SSP to be reinitialized:
clear sse
Use the ethernet-transit-oui interface configuration command to choose the Organizational Unique Identifier (OUI) code to be used in the encapsulation of Ethernet Type II frames across Token Ring backbone networks. Various versions of this OUI code are used by Ethernet/Token Ring translational bridges. The default OUI form is 90-compatible, which can be chosen with the no form of the command.
ethernet-transit-oui [90-compatible | standard | cisco]| 90-compatible | (Optional) Default OUI form |
| standard | (Optional) Standard OUI form |
| cisco | (Optional) Cisco's OUI form |
Interface configuration
This command replaces and extends the bridge old-oui command in release 9.0.
The actual OUI codes that are used, when they are used, and how they compare to Software Release 9.0-equivalent commands is shown in Table 21-1.
| Keyword | OUI Used | When Used/Benefits | 9.0 Command Equivalent |
|---|---|---|---|
| 90-compatible | 0000F8 | By default, when talking to other Cisco routers. Provides the most flexibility. | no bridge old-oui |
| cisco | 00000C | Provided for compatibility with future equipment. | None |
| standard | 000000 | When talking to IBM 8209 bridges and other vendor equipment. Does not provide for as much flexibility as the other two choices. | bridge old-oui |
Do not use the keyword standard unless you are forced to interoperate with other vendor equipment, such as the IBM 8209, in providing Ethernet and Token Ring mixed media bridged connectivity. The use of the standard OUI of 000000 in the encapsulation of Ethernet Type II frames creates encapsulated frames on Token Rings that have formats identical to SNAP-encapsulated frames. The router receiving such a frame on a Token Ring for delivery on the Ethernet cannot distinguish between the two, and therefore must make an arbitrary choice between presenting the frame on the Ethernet as a SNAP-encapsulated frame or as an Ethernet Type II frame. The choice has been made to present all such frames as Ethernet Type II. Therefore, it is impossible to use the standard keyword if you wish to bridge SNAP-encapsulated frames between Token Rings and Ethernets. Using either the cisco or 90-compatible keywords does not present such a restriction, because SNAP frames and Ethernet Type II-encapsulated frames have different OUI codes on Token Ring networks.
The following example specifies Cisco's OUI form:
interface tokenring 0
ethernet-transit-oui cisco
bridge-group
bridge protocol
Use the frame-relay map bridge broadcast interface configuration command to bridge over a Frame Relay network. Use the no form of this command to delete the mapping entry.
frame-relay map bridge dlci broadcast| dlci | DLCI number. The valid range is 16 to 1007. |
No mapping entry is established.
Interface configuration
Bridging over a Frame Relay network is supported both on networks that support a multicast facility and those that do not.
The following example allows bridging over a Frame Relay network:
frame-relay map bridge 144 broadcast
A dagger (+) indicates that the command is documented in another chapter.
encapsulation frame-relay +
Use the ip routing command to enable IP routing. Use the no ip routing global configuration command to disable IP routing so that you can then bridge IP.
ip routingThis command has no arguments or keywords.
IP routing
Global configuration
All protocols except IP are bridged by a router/bridge unless their routing is explicitly enabled. Refer to the "IP Commands" chapter of this manual for the procedures to enable routing of individual protocols. IP is normally routed by the router/bridge.
Also note that bridging and routing are done on a per-system basis. If a protocol is being routed, it must be routed on all interfaces that are handling that protocol. This is similar for bridging. You cannot route IP on one interface and bridge it on another interface.
Assign the same IP address to all network interfaces to manage the system with Telnet, TFTP, SNMP, ICMP (ping), and so forth. Once bridging is enabled, all IP and ARP frames are forwarded or flooded by the router/bridge according to standard bridging and spanning-tree rules. IP routing processes such as IGRP or RIP must not be running.
The following example disables IP routing:
no ip routing
Use the show bridge privileged EXEC command to view classes of entries in the bridge forwarding database.
show bridge [bridge-group] [interface]| bridge-group
| (Optional) Number you chose that specifies a particular spanning tree. |
| interface | (Optional) Specific interface, such as Ethernet 0. |
| address | (Optional) 48-bit canonical (Ethernet ordered) MAC address. This may be entered with an optional mask of bits to be ignored in the address, which is specified with the mask argument. |
| mask | (Optional) Bits to be ignored in the address. You must specify the address argument if you want to specify a mask. |
Privileged EXEC
The following is sample output of the show bridge command strings:
router# show bridge
show bridge ethernet 0
show bridge 0000.0c00.0000 0000.00FF.FFFF
show bridge 0000.0c00.0e1a
show bridge
In the sample output, the first command would display all entries for hosts reachable via interface Ethernet 0, the second command would display all entries with the vendor code of 0000.0c00.0000, and the third command would display the entry for address 0000.0c00.0e1a. In the fourth command, all entries in the forwarding database would be displayed. In all four examples, the bridge group number has been omitted.
The following is sample output from the show bridge command:
router# show bridge
Total of 300 station blocks, 295 free
BG Hash Address Action Interface Age RX count TX count
1 00/0 FFFF.FFFF.FFFF discard - P 0 0
1 09/0 0000.0C00.0009 forward Ethernet0 0 2 0
1 49/0 0000.0C00.4009 forward Ethernet0 0 1 0
1 CA/0 AA00.0400.06CC forward Ethernet0 0 25 0
Table 21-2 describes significant fields shown in the display.
| Field | Description |
|---|---|
| Total of 300 station blocks | Total number of forwarding database elements in the system. The memory to hold bridge entries is allocated in blocks of memory sufficient to hold 300 individual entries. When the number of free entries falls below 25, another block of memory sufficient to hold another 300 entries is allocated. Therefore, the size of the bridge forwarding database is limited to the amount of free memory in the router. |
| 295 free | Number in the free list of forwarding database elements in the system. The total number of forwarding elements is expanded dynamically, as needed. |
| BG | Bridging group to which the address belongs. |
| Hash | Hash key/relative position in the keyed list. |
| Address | Canonical (Ethernet ordered) MAC address. |
| Action | Action to be taken when that address is looked up; choices are to discard or forward the datagram. |
| Interface | Interface, if any, on which that address was seen. |
| Age | Number of minutes since a frame was received from or sent to that address. The letter "P" indicates a permanent entry. The letter "S" indicates the system as recorded by the router. On the modular systems, this is typically the broadcast address and the router's own hardware address; on the IGS, this field will also include certain multicast addresses. |
| RX count | Number of frames received from that address. |
| TX count | Number of frames forwarded to that address. |
Use the show bridge circuit-group EXEC command to display the interfaces configured in each circuit group and show whether they are currently participating in load distribution.
show bridge [bridge-group] circuit-group [circuit-group] [src-mac-address]| bridge-group | (Optional) Number that specifies a particular bridge group. |
| circuit-group | (Optional) Number that specifies a particular circuit group. |
| src-mac-address | (Optional) 48-bit canonical (Ethernet ordered) source MAC address. |
| dst-mac-address | (Optional) 48-bit canonical (Ethernet ordered) destination MAC address. |
EXEC
The following is sample output of various show bridge circuit-group command strings:
routerA> show bridge circuit-group
Bridge group 1 Circuit group 1:
Interface Serial0 : inserted, learning, forwarding
Interface Serial3 : inserted, learning, forwarding
Bridge group 1 Circuit group 2:
Interface Serial2 : inserted, learning, forwarding
routerA> show bridge 1 circuit-group 1
Bridge group 1 Circuit group 1:
Interface Serial0 : inserted, learning, forwarding
Interface Serial3 : inserted, learning, forwarding
routerA> show bridge 1 circuit-group 2
Bridge group 1 Circuit group 2:
Interface Serial2 : inserted, learning, forwarding
routerA> show bridge 1 circuit-group 1 0000.6502.23EA 0000.1234.4567
Output circuit group interface is Serial3
routerA> show bridge 1 circuit-group 1 0000.6502.23EA
%Destination MAC address required
routerB> show bridge 1 circuit-group 1
Bridge group 1 Circuit group 1:
Transmission pause interval is 250ms
Output interface selection is source-based
Interface Serial0 : inserted, learning, forwarding
Interface Serial3 : inserted, learning, forwarding
Interface Serial2 is unavailable
routerB> show bridge 1 circuit-group 1 0000.6502.23EA 0000.1234.4567
%Please enter source MAC address only
Table 21-3 describes significant fields shown in the display.
| Field | Description |
| inserted/not inserted | Indicates whether interface is included or not included in circuit-group operation. If the interface is administratively down, or if line protocol is not up, the interface is not included in the circuit-group operation. |
| learning/not learning | Indicates whether this interface is in spanning tree protocol (IEEE or DEC) learning or not learning state. |
| forwarding/not forwarding | Indicates whether this port is in spanning tree protocol (IEEE or DEC) forwarding or not forwarding state |
Use the show span privileged EXEC command to display the spanning-tree topology known to the router/bridge. The display indicates whether LAT group code filtering is in effect.
show spanThis command has no arguments or keywords.
Privileged EXEC
The following bridge-group commands are incompatible with autonomous bridging:
bridge-group input-type-list
bridge-group output-type-list
bridge-group input-lsap-list
bridge-group output-lsap-list
bridge-group input-pattern
bridge-group output-pattern
bridge-group input-lat-service-deny
bridge-group input-lat-service-permit
bridge-group output-lat-service-deny
bridge-group output-lat-service-permit
bridge-group lat-compression
bridge-group circuit
The following is sample output for the show span command when the router is the root of the spanning tree.
As the sample display shows, the first part of the show span output lists global spanning-tree configuration parameters, followed by those that are specific to given interfaces.
Explanations for representative lines of output in the display follow.
The first line of output indicates which type of spanning tree protocol (IEEE or DEC) the bridge group is executing:
Bridge Group 1 is executing the IEEE compatible spanning tree protocol
The following lines of output show the current operating parameters of the spanning tree. For more information, refer to the IEEE Standard 802.1D-1990.
IEEE bridge domains are not used for this bridge group
Bridge Identifier has priority 32768, address 0000.0c00.ab40
Configured hello time 2, max age 20, forward delay 15
The following line of output shows that the router is the root of the spanning tree:
We are the root of the spanning tree
The following lines of output have nothing to do with the spanning tree protocol, but are included in show span output for convenience, so that the user can avoid using the write terminal command to find out this information:
Acquisition of new addresses is enabled
Forwarding of multicast source addresses is disabled
LAT service filtering is disabled
The following lines of output show additional current operating parameters of the spanning tree. For more information, refer to the IEEE Standard 802.1D-1990.
Topology change flag not set, detected flag not set
Times: hold 1, topology change 30, notification 30
hello 2, max age 20, forward delay 15
Timers: hello 2, topology change 0, notification 0
Table 21-4 describes the fields in the following line of output.
Port 1 (Ethernet0) of bridge group 1 is forwarding. Path cost 100, priority 0
| Field | Description |
|---|---|
| Port 1 | Port number associated with the interface. The port number and the port priority form the port ID. |
| (Ethernet0) | Interface on which Translational Bridging has been configured. |
| of bridge group 1 | Bridge group to which the interface has been assigned. |
| is forwarding | State of the interface. Possible values follow:
|
|
Path cost 100 | Path cost associated with the interface, as determined by default, or using the bridge-group path cost command. |
| priority 0 | Port priority. |
The following lines of output show the priority and the MAC address. Together they form the Root Identifier and the Bridge Identifier, respectively.
Designated root has priority 32768, address 0000.0c00.ab40
Designated bridge has priority 32768, address 0000.0c00.ab40
The following lines of output are self-explanatory:
Designated port is 1, path cost 0
Timers: message age 0, forward delay 0, hold 0
The following lines of output have nothing to do with the spanning tree protocol, but are included in show span output for convenience, so that the user can avoid using the write terminal command to find out this information:
LAT compression is not set
Input LAT service deny group code list is not set
Input LAT service permit group code list is not set
Output LAT service deny group code list is not set
Output LAT service permit group code list is not set
Access list for input filtering on type is not set; for LSAP is not set
Access list for input address filter is not set
Access list for input pattern is not set
Access list for output filtering on type is not set; for LSAP is not set
Access list for output address filter is not set
Access list for output pattern filter is not set
The following line of output indicates the number of packets destined for an interface which have been discarded by the bridge because they are larger than the MTU for the output media:
Packets too large for translational bridging: 0 input, 0 output
The following line of output indicates that autonomous bridging is enabled and no other incompatible bridge group commands have been defined:
Autonomous bridging is enabled
If autonomous bridging is configured on an interface and one or more incompatible bridge group commands have been defined the following line of output displays:
Autonomous bridging is suppressed
The following is a sample output from show span command when the router is not the root of the spanning tree.
This sample show span output is similar to the show span output for a router acting as the spanning tree root, except for the following lines of output.
The following line of output indicates that the root at address 0000.0c00.ab40 has a priority of 32768:
Current root has priority 32768, address 0000.0c00.ab40
The following line of output indicates the root port and the path cost:
Root port is 1 (Ethernet0), cost of root path is 100
Use the show sse summary EXEC command to display a summary of Silicon Switch Processor (SSP) statistics:
show sse summaryThis command has no arguments or keywords.
EXEC
The following is sample output from the show sse summary command:
Router# show sse summary
SSE utilization statistics
Program words Rewrite bytes Internal nodes Depth
Overhead 499 1 8
IP 0 0 0 0
IPX 0 0 0 0
SRB 0 0 0 0
CLNP 0 0 0 0
IP access lists 0 0 0
Total used 499 1 8
Total free 65037 262143
Total available 65536 262144
Free program memory
[499..65535]
Free rewrite memory
[1..262143]
Internals
75032 internal nodes allocated, 75024 freed
SSE manager process enabled, microcode enabled, 0 hangs
Longest cache computation 4ms, longest quantum 160ms at 0x53AC8
Use the x25 map bridge broadcast interface configuration command to configure the bridging of packets in X.25 frames. Use the no form of this command to disable the Internet-to-X.121 mapping.
x25 map bridge x.121-address broadcast [options-keywords]| x.121-address | The X.121 address. |
| options-keywords | (Optional) The services that can be added to this map; these services are listed in the section "Setting Address Mappings" in the Router Products Configuration Guide. |
Disabled
Interface configuration
The X.25 bridging software uses the same spanning-tree algorithm as the other bridging functions, but allows packets to be encapsulated in X.25 frames and transmitted across X.25 media. This command specifies Internet-to-X.121 address mapping and maintains a table of both the Ethernet and X.121 addresses.
The following example allows bridging over an X.25 network:
x25 map bridge 31370054065 broadcast
x25 address
|
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