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Router Products Command Reference
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About This Manual
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Router Product Overview
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User Interface Commands
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System Image, Microcode Image, and Configuration File Load Comm
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Terminal Line and Modem Support Commands
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System Management Commands
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Interface Commands
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ATM Commands
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DDR Commands
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Frame Relay Commands
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ISDN Commands
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LAN Emulation Commands
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SMDS Commands
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X.25 Commands
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Apollo Domain Commands
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AppleTalk Commands
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Banyan VINES Commands
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DECnet Commands
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IP Commands
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IP Routing Protocols Commands
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ISO CLNS Commands
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Novell IPX Commands
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XNS Commands
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Source-Route Bridging Commands
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Remote Source-Route Bridging Commands
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DLSw+ Configuration Commands
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STUN and BSTUN Configuration Commands
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LLC2 and SDLC Configuration Commands
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IBM Network Media Translation Commands
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DSPU and SNA Service Point Configuration Commands
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SNA Frame Relay Access Support Commands
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APPN Configuration Commands
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IBM Channel Attach Configuration Commands
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References and Recommended Reading
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Ethernet Type Codes
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Regular Expressions
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ASCII character Set
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Platform Support
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Switching Appendix
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Table Of Contents
default-information originate (BGP)
default-information originate (EGP)
default-information originate (IS-IS)
default-information originate (OSPF)
default-metric (BGP, EGP, OSPF, and RIP)
default-metric (IGRP and Enhanced IGRP only)
ip dvmrp routehog-notification
neighbor advertisement-interval
neighbor peer-group (creating)
neighbor peer-group (assigning members)
network (IGRP and Enhanced IGRP)
show ip ospf retransmission-list
IP Routing Protocols Commands
Cisco's implementation of the Internet Protocol (IP) suite provides all major services contained in the TCP/IP specifications.
Use the commands in this chapter to configure and monitor the IP routing protocols. For IP routing protocol configuration information and examples, refer to the "Configuring IP Routing Protocols" chapter of the Router Products Configuration Guide.
aggregate-address
To create an aggregate entry in a BGP routing table, use the aggregate-address router configuration command. To disable this feature, use the no form of this command.
aggregate-address address mask [as-set] [summary-only] [suppress-map map-name]
[advertise-map map-name] [attribute-map map-name]
no aggregate-address address mask [as-set] [summary-only] [suppress-map map-name]
[advertise-map map-name] [attribute-map map-name]Syntax Description
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
You can implement aggregate routing in BGP either by redistributing an aggregate route into BGP or by using this conditional aggregate routing feature.
Using the aggregate-address command with no arguments will create an aggregate entry in the BGP routing table if there are any more-specific BGP routes available that fall in the specified range. The aggregate route will be advertised as coming from your autonomous system and has the atomic aggregate attribute set to show that information might be missing. (By default, the atomic aggregate attribute is set unless you specify the as-set keyword.)
Using the as-set keyword creates an aggregate entry using the same rules that the command follows without this keyword, but the path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized. Do not use this form of aggregate-address when aggregating many paths, because this route must be continually withdrawn and re-updated as autonomous system path reachability information for the summarized routes changes.
Using the summary-only keyword not only creates the aggregate route (for example, 193.*.*.*) but will also suppress advertisements of more specific routes to all neighbors. If you only want to suppress advertisements to certain neighbors, you may use the neighbor distribute-list command, with caution. If a more specific route leaks out, all BGP speakers will prefer that route over the less specific aggregate you are generating (using longest-match routing).
Using the suppress-map keyword creates the aggregate route but suppresses advertisement of specified routes. You can use the match clauses of route maps to selectively suppress some more specific routes of the aggregate and leave others unsuppressed. IP access lists and autonomous system path access lists match clauses are supported.
Example
In the following example, an aggregate address is created. The path advertised for this route will be an AS_SET consisting of all elements contained in all paths that are being summarized.
router bgp 5aggregate-address 193.0.0.0 255.0.0.0 as-setRelated Commands
match as-path
match ip address
route-maparea authentication
To enable authentication for an OSPF area, use the area authentication router configuration command. To remove an area's authentication specification or a specified area from the router's configuration, use the no form of this command.
area area-id authentication [message-digest]
no area area-id authentication
no area area-idSyntax Description
Default
Type 0 authentication (no authentication)
Command Mode
Router configuration
Usage Guidelines
Specifying authentication for an area sets the authentication to Type 1 (simple password) as specified in RFC 1247. If this command is not included in the configuration file, authentication of Type 0 (no authentication) is assumed.
The authentication type must be the same for all routers in an area. The authentication password for all OSPF routers on a network must be the same if they are to communicate with each other via OSPF. Use the ip ospf authentication-key command to specify this password.
If you enable MD5 authentication with the message-digest keyword, you must configure a password with the ip ospf message-digest-key command.
To remove the area's authentication specification, use the no form of this command with the authentication keyword. To remove the specified area from the router's configuration, use the command no area area-id (with no other keywords).
Example
The following example mandates authentication for areas 0 and 36.0.0.0 of OSPF routing process 201. Authentication keys are also provided.
interface ethernet 0ip address 131.119.251.201 255.255.255.0ip ospf authentication-key adcdefgh!interface ethernet 1ip address 36.56.0.201 255.255.0.0ip ospf authentication-key ijklmnop!router ospf 201network 36.0.0.0 0.255.255.255 area 36.0.0.0network 131.119.0.0 0.0.255.255 area 0area 36.0.0.0 authenticationarea 0 authenticationRelated Commands
area default-cost
area stub
ip ospf authentication-key
ip ospf message-digest-keyarea default-cost
To specify a cost for the default summary route sent into a stub area, use the area default-cost router configuration command. To remove the assigned default route cost, use the no form of this command.
area area-id default-cost cost
no area area-id default-cost costSyntax Description
Default
Cost of 1
Command Mode
Router configuration
Usage Guidelines
This command is used only on an area border router attached to a stub area.
There are two stub area router configuration commands: the stub and default-cost options of the area command. In all routers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an area border router attached to the stub area. The default-cost option provides the metric for the summary default route generated by the area border router into the stub area.
Example
The following example assigns a default-cost of 20 to stub network 36.0.0.0:
interface ethernet 0ip address 36.56.0.201 255.255.0.0!router ospf 201network 36.0.0.0 0.255.255.255 area 36.0.0.0area 36.0.0.0 stubarea 36.0.0.0 default-cost 20Related Commands
area-password
To configure the IS-IS area authentication password, use the area-password router configuration command. To disable the password, use the no form of this command.
area-password password
no area-password [password]Syntax Description
Default
No area password is defined.
Command Mode
Router configuration
Usage Guidelines
This password is inserted in Level 1 (station router level) link state PDUs (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNP).
Example
The following example assigns an area authentication password:
router isisarea-password angelRelated Command
area range
To consolidate and summarize routes at an area boundary, use the area range router configuration command. To disable this function, use the no form of this command.
area area-id range address mask
no area area-id range address maskSyntax Description
area-id
Identifier of the area about which routes are to be summarized. It can be specified as either a decimal value or as an IP address.
address
IP address.
mask
IP mask.
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
The area range command is used only with area border routers. It is used to consolidate or summarize routes for an area. The result is that a single summary route is advertised to other areas by the area border router. Routing information is condensed at area boundaries. External to the area, a single route is advertised for each address range. This is called route summarization.
Multiple area router configuration commands specifying the range option can be configured. Thus, OSPF can summarize addresses for many different sets of address ranges.
Example
The following example specifies one summary route to be advertised by the area border router to other areas for all subnets on network 36.0.0.0 and for all hosts on network 192.42.110.0:
interface ethernet 0ip address 192.42.110.201 255.255.255.0!interface ethernet 1ip address 36.56.0.201 255.255.0.0!router ospf 201network 36.0.0.0 0.255.255.255 area 36.0.0.0network 192.42.110.0 0.0.0.255 area 0area 36.0.0.0 range 36.0.0.0 255.0.0.0area 0 range 192.42.110.0 255.255.255.0area stub
To define an area as a stub area, use the area stub router configuration command. To disable this function, use the no form of this command.
area area-id stub [no-summary]
no area area-id stubSyntax Description
Default
No stub area is defined.
Command Mode
Router configuration
Usage Guidelines
You must configure the area stub command on all routers in the stub area. Use the area router configuration command with the default-cost option to specify the cost of a default internal router sent into a stub area by an area border router.
There are two stub area router configuration commands: the stub and default-cost options of the area router configuration command. In all routers attached to the stub area, the area should be configured as a stub area using the stub option of the area command. Use the default-cost option only on an area border router attached to the stub area. The default-cost option provides the metric for the summary default route generated by the area border router into the stub area.
To further reduce the number of link state advertisements (LSA) sent into a stub area, you can configure no-summary on the Area Border Router (ABR) to prevent it from sending summary link advertisement (LSA type 3) into the stub area.
Example
The following example assigns a default cost of 20 to stub network 36.0.0.0:
interface ethernet 0ip address 36.56.0.201 255.255.0.0!router ospf 201network 36.0.0.0 0.255.255.255 area 36.0.0.0area 36.0.0.0 stubarea 36.0.0.0 default-cost 20Related Commands
area authentication
area default-costarea virtual-link
To define an OSPF virtual link, use the area virtual-link router configuration command with the optional parameters. To remove a virtual link, use the no form of this command.
area area-id virtual-link router-id [hello-interval seconds] [retransmit-interval seconds]
[transmit-delay seconds] [dead-interval seconds] [[authentication-key key] |
[message-digest-key keyid md5 key]]
no area area-id virtual-link router-id [hello-interval seconds] [retransmit-interval seconds]
[transmit-delay seconds] [dead-interval seconds] [[authentication-key key] |
[message-digest-key keyid md5 key]]Syntax Description
Default
area-id: No area ID is predefined.
router-id: No router ID is predefined.
hello-interval seconds: 10 seconds
retransmit-interval seconds: 10 seconds
transmit-delay seconds: 1 second
dead-interval seconds: 40 seconds
authentication-key key: No key is predefined.
message-digest-key keyid md5 key: No key is predefined.Command Mode
Router configuration
Usage Guidelines
In OSPF, all areas must be connected to a backbone area. If the connection to the backbone is lost, it can be repaired by establishing a virtual link.
The smaller the Hello interval, the faster topological changes will be detected, but more routing traffic will ensue.
The setting of the retransmit interval should be conservative, or needless retransmissions will result. The value should be larger for serial lines and virtual links.
The transmit delay value should take into account the transmission and propagation delays for the interface.
A router will use the specified authentication key only when authentication is enabled for the backbone with the area area-id authentication router configuration command.
The two authentication schemes, simple text and MD5 authentication, are mutually exclusive. You can specify one or the other or neither. Any keywords and arguments you specify after authentication-key key or message-digest-key keyid md5 key are ignored. Therefore, specify any optional arguments before such a keyword-argument combination.
Note
Each virtual link neighbor must include the transit area ID and the corresponding virtual link neighbor's router ID in order for a virtual link to be properly configured. Use the show ip ospf EXEC command to see the router ID of a router.
Examples
The following example establishes a virtual link with default values for all optional parameters:
router ospf 201network 36.0.0.0 0.255.255.255 area 36.0.0.0area 36.0.0.0 virtual-link 36.3.4.5The following example establishes a virtual link with MD5 authentication:
router ospf 201network 36.0.0.0 0.255.255.255 area 36.0.0.0area 36.0.0.0 virtual-link 36.3.4.5 message-digest-key 3 md5 sa5721bk47Related Commands
A dagger (†) indicates that the command is documented in another chapter.
area authentication
service password-encryption †
show ip ospfautonomous-system (EGP)
To specify the local autonomous system that the router resides in for EGP, use the autonomous-system global configuration command. To remove the autonomous system number, use the no form of this command.
autonomous-system local-as
no autonomous-system local-asSyntax Description
Default
No local autonomous system is specified.
Command Mode
Global configuration
Usage Guidelines
Before you can set up EGP routing, you must specify an autonomous system number. The local autonomous system number will be included in EGP messages sent by the router.
Example
The following sample configuration specifies an autonomous system number of 110:
autonomous-system 110Related Command
auto-summary
To restore the default behavior of automatic summarization of subnet routes into network-level routes, use the auto-summary router configuration command. To disable this feature, use the no form of this command.
auto-summary
no auto-summarySyntax Description
This command has no arguments or keywords.
Default
Enabled
Command Mode
Router configuration
Usage Guidelines
By default, BGP does not accept subnets redistributed from IGP. To advertise and carry subnet routes in BGP, use an explicit network command or the no auto-summary command. If you disable auto-summarization and have not entered a network command, you will not advertise network routes for networks with subnet routes unless they contain a summary route.
IP Enhanced IGRP summary routes are given an administrative distance value of 5. You cannot configure this value.
Examples
In the following example, network numbers are not summarized automatically:
router bgp 6no auto-summaryThe following example disables automatic summarization for router process eigrp 109:
router eigrp 109no auto-summaryRelated Command
bgp always-compare-med
To allow the comparison of the Multi Exit Discriminator (MED) for paths from neighbors in different autonomous systems, use the bgp always-compare-med router configuration command. To disallow the comparison, use the no form of this command.
bgp always-compare-med
no bgp always-compare-medSyntax Description
This command has no arguments or keywords.
Default
The router does not compare MEDs for paths from neighbors in different autonomous systems.
Command Mode
Router configuration
Usage Guidelines
The MED is one of the parameters that is considered when selecting the best path among many alternative paths. The path with a lower MED is preferred over a path with a higher MED.
By default, during the best path selection process, MED comparision is done only among paths from the same autonomous system. This command changes the default behavior by allowing comparision of MEDs among paths regardless of the autonomous system from which the paths are received.
Example
In the following example, the BGP speaker in autonomous system 100 is configured to compare MEDs among alternative paths, regardless of the autonomous system from which the paths are received:
router bgp 109bgp always-compare-medbgp confederation identifier
To specify a BGP confederation identifier, use the bgp confederation identifier router configuration command. To remove the confederation identifier, use the no form of this command.
bgp confederation identifier autonomous-system
no bgp confederation identifier autonomous-systemSyntax Description
Default
No confederation identifier is configured.
Command Mode
Router configuration
Usage Guidelines
Another way to reduce the IBGP mesh is to divide an autonomous system into multiple autonomous systems and group them into a single confederation. Each autonomous system is fully meshed within itself, and has a few connections to another autonomous system in the same confederation. Even though the peers in different autonomous systems have EBGP sessions, they exchange routing information as if they are IBGP peers. Specifically, the next-hop and local preference information is preserved. This enables to you to retain a single Interior Gateway Protocol (IGP) for all of the autonomous systems. To the outside world, the confederation looks like a single autonomous system.
Example
In the following example, the autonomous system is divided into autonomous systems 4001, 4002, 4003, 4004, 4005, 4006, and 4007 and identified by the confederation identifier 5. Neighbor 1.2.3.4 is someone inside your routing domain confederation. Neighbor 3.4.5.6 is someone outside your routing domain confederation. To the outside world, there appears to be a single autonomous system with the number 5.
router bgp 4001bgp confederation identifier 5bgp confederation peers 4002 4003 4004 4005 4006 4007neighbor 1.2.3.4 remote-as 4002neighbor 3.4.5.6 remote-as 510Related Command
bgp confederation peers
To configure the autonomous systems that belong to the confederation, use the bgp confederation peers router configuration command. To remove an autonomous system from the confederation, use the no form of this command.
bgp confederation peers autonomous-system [autonomous-system]
no bgp confederation peers autonomous-system [autonomous-system]Syntax Description
Default
No confederation peers are configured.
Command Mode
Router configuration
Usage Guidelines
The autonomous systems specified in this command are visible internally to a confederation. Each autonomous system is fully meshed within itself. The bgp confederation identifier command specifies the confederation that the autonomous systems belong to.
Example
The following example specifies that autonomous systems 1090, 1091, 1092, and 1093 belong to a single confederation:
router bgp 1090bgp confederation peers 1091 1092 1093Related Command
bgp default local-preference
To change the default local preference value, use the bgp default local-preference router configuration command. To return to the default setting, use the no form of this command.
bgp default local-preference value
no bgp default local-preference valueSyntax Description
Default
Local preference value of 100
Command Mode
Router configuration
Usage Guidelines
Generally, the default value of 100 allows you to easily define a particular path as less preferable than paths with no local preference attribute. The preference is sent to all routers in the local autonomous system.
Example
In the following example, the default local preference value is raised from the default of 100 to 200:
router bgp 200bgp default local-preference 200Related Command
bgp fast-external-fallover
To immediately reset the BGP sessions of any directly adjacent external peers if the link used to reach them goes down, use the bgp fast-external-fallover router configuration command. To disable this feature, use the no form of this command.
bgp fast-external-fallover
no bgp fast-external-falloverSyntax Description
This command has no arguments or keywords.
Default
Enabled
Command Mode
Router configuration
Example
In the following example, the automatic resetting of BGP sessions is disabled:
router bgp 109no bgp fast-external-falloverbgp log-neighbor-changes
To enable logging of BGP neighbor resets, use the bgp log-neighbor-changes router configuration command. To disable the logging of changes in BGP neighbor adjacencies, use the no form of this command.
bgp log-neighbor-changes
no bgp log-neighbor-changesSyntax Description
This command has no arguments or keywords.
Default
No BGP neighbor changes are logged.
Command Mode
Router configuration
Usage Guidelines
The bgp log-neighbor-changes command enables logging of BGP neighbor status changes (up or down) and resets for troubleshooting network connectivity problems and measuring network stability. Unexpected neighbor resets might indicate high error rates or high packet loss in the network and should be investigated.
Using the bgp log-neighbo-changes command to enable status change message logging does not create a significant performance hit, unlike, for example, enabling per BGP update debugging. If the UNIX syslog facility is enabled, messages are sent to the UNIX host running the syslog daemon so that the messages can be stored and archived. If the UNIX syslog facility is not enabled, the status change messages are retained in the router's internal buffer, and are not stored to disk. You can set the size of this buffer, which is dependent upon the available RAM, using the logging buffered command.
The neighbor status change messages are not tracked if bgp log-neighbor changes is not enabled, except for the reset reason, which is always available as output of the show ip bgp neighbor command.
The log messages display the following reasons for changes in a neighbor's status:
BGP protocol initialization
No memory for path entry
No memory for attribute entry
No memory for prefix entry
No memory for aggregate entry
No memory for dampening info
No memory for BGP updates
BGP Notification received
Erroneous BGP Update received
User reset request
Peer timeout
Password change
Error during connection collision
Peer closing down the session
Peer exceeding maximum prefix limit
Interface flap
Router ID changed
Neighbor deleted
Member added to peergroup
Administratively shutdown
Remote AS changed
RR client configuration modification
Soft reconfiguration modification
The eigrp log-neighbor-changes command enables logging of Enhanced IGRP neighbor adjacencies, but messages for BGP neighbors are logged only if they are specifically enabled with the bgp log-neighbor-changes command.
Use the show logging command to display the log for the BGP neighbor changes.
Example
The following configuration will log neighbor changes for BGP:
bgp router 100bgp log-neighbor-changes
Related Commands
You can use the master indexes or search online to find documentation of related commands.
logging buffered
show ip bgp neighbor
show loggingclear arp-cache
To remove all dynamic entries from the ARP cache and to clear the fast-switching cache, use the clear arp-cache EXEC command.
clear arp-cache
Syntax Description
This command has no arguments or keywords.
Command Mode
EXEC
Example
The following example removes all dynamic entries from the ARP cache and clears the fast-switching cache:
clear arp-cacheclear ip bgp
To reset a BGP connection, use the clear ip bgp EXEC command at the system prompt.
clear ip bgp {* | address}
Syntax Description
Command Mode
EXEC
Usage Guidelines
Use this command whenever any of the following changes occur:
•
•
•
•
•
•
Example
The following example resets all current BGP sessions:
clear ip bgp *Related Commands
clear ip bgp peer-group
To remove all of the members of a BGP peer group, use the clear ip bgp peer-group EXEC command.
clear ip bgp peer-group tag
Syntax Description
Command Mode
EXEC
Example
The following example removes all members from the BGP peer group internal:
clear ip bgp peer-group internalRelated Command
neighbor peer-group (assigning members)
clear ip dvmrp route
To delete routes from the DVMRP routing table, use the clear ip dvmrp route EXEC command.
clear ip dvmrp route {* | route}
Syntax Description
*
Clears all routes.
route
Clears the longest matched route. Can be an IP address, a network number, or an IP DNS name.
Command Mode
EXEC
Examples
The following example deletes route 10.1.1.1 from the DVMRP routing table:
clear ip dvmrp route 10.1.1.1The following example deletes network 10.0.0.0 from the DVMRP routing table:
clear ip dvmrp route 10.0.0.0clear ip eigrp neighbors
To delete entries from the neighbor table, use the clear ip eigrp neighbors EXEC command.
clear ip eigrp neighbors [ip-address | type number]
Syntax Description
ip-address
(Optional) Address of the neighbor.
type number
(Optional) Interface type and number. Specifying these arguments removes from the neighbor table all entries learned via this interface.
Command Mode
EXEC
Example
The following example removes the neighbor whose address is 160.20.8.3:
clear ip eigrp neighbors 160.20.8.3Related Command
clear ip igmp group
To delete entries from the IGMP cache, use the clear ip igmp group EXEC command.
clear ip igmp group [group-name | group-address | type number]
Syntax Description
Command Mode
EXEC
Usage Guidelines
The IGMP cache contains a list of the multicast groups of which hosts on the directly connected LAN are members. If the router has joined a group, it is also listed in the cache.
To delete all entries from the IGMP cache, specify the clear ip igmp group command with no arguments.
Example
The following example clears entries for the multicast group 224.0.255.1 from the IGMP cache:
clear ip igmp group 224.0.255.1Related Commands
A dagger (†) indicates that the command is documented in another chapter.
ip host †
show ip igmp groups
show ip igmp interfaceclear ip mroute
To delete entries from the IP multicast routing table, use the clear ip mroute EXEC command.
clear ip mroute {* | group [source]}
Syntax Description
Command Mode
EXEC
Examples
The following example deletes all entries from the IP multicast routing table:
clear ip mroute *The following example deletes from the IP multicast routing table all sources on the 10.3.0.0 subnet that are transmitting to the multicast group 224.2.205.42. Note that this example deletes all sources on network 10.3, not individual sources.
clear ip mroute 224.2.205.42 10.3.0.0Related Commands
A dagger (†) indicates that the command is documented in another chapter.
ip host †
show ip mrouteclear ip route
To remove one or more routes from the IP routing table, use the clear ip route EXEC command.
clear ip route {network [mask] | *}
Syntax Description
network
Network or subnet address to remove.
mask
(Optional) Network mask associated with the IP address you wish to remove.
*
Removes all entries.
Command Mode
EXEC
Example
The following example removes a route to network 132.5.0.0 from the IP routing table:
clear ip route 132.5.0.0Related Command
clear ip sd
To delete a session directory cache entry, use the clear ip sd EXEC command.
clear ip sd [group-address | "session-name"]
Syntax Description
Command Mode
EXEC
Usage Guidelines
If neither argument is specified, the entire session directory cache is deleted.
Examples
The following example deletes the entire session directory cache:
clear ip sdThe following example deletes sessions with the group address 224.2.0.1 from the session directory cache:
clear ip sd 224.2.0.1The following example deletes the session entry called mbone audio from the session directory cache:
clear ip sd "mbone audio"Related Command
default-information allowed
To control the candidate default routing information between IGRP or Enhanced IGRP processes, use the default-information allowed router configuration command. To suppress IGRP or Enhanced IGRP candidate information in incoming updates, use the no default-information allowed in command. To suppress IGRP or Enhanced IGRP candidate information in outbound updates, use the no default-information allowed out command.
default-information allowed {in | out} [route-map map-tag]
no default-information allowed {in | out} [route-map map-tag]Syntax Description
Default
Normally, exterior routes are always accepted and default information is passed between IGRP or Enhanced IGRP processes when doing redistribution.
Command Mode
Router configuration
Usage Guidelines
The default network of 0.0.0.0 used by RIP cannot be redistributed by IGRP or Enhanced IGRP.
Example
The following example allows IGRP exterior or default routes to be received by the IGRP process in autonomous system 23:
router igrp 23default-information allowed indefault-information originate (BGP)
To allow the redistribution of network 0.0.0.0 into BGP, use the default-information originate router configuration command. To disable this feature, use the no form of this command.
default-information originate
no default-information originateSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
The same functionality will result from the network 0.0.0.0 command, using the network router configuration command.
Example
The following example configures BGP to redistribute network 0.0.0.0 into BGP:
router bgp 164default-information originatedefault-information originate (EGP)
To explicitly configure EGP to generate a default route, use the default-information originate router configuration command. To disable this feature, use the no form of this command.
default-information originate
no default-information originateSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
Because EGP can use network 0.0.0.0 as a default route, EGP must be explicitly configured to generate a default route. If the next hop for the default route can be advertised as a third party, it will be included as a third party.
Example
The following example configures EGP to generate a default route:
autonomous system 109router egp 164network 131.108.0.0network 192.31.7.0neighbor 10.2.0.2default-information originatedefault-information originate (IS-IS)
To generate a default route into an IS-IS routing domain, use the default-information originate router configuration command. To disable this feature, use the no form of this command.
default-information originate [route-map map-name]
no default-information originate [route-map map-name]Syntax Description
route-map map-name
(Optional) Routing process will generate the default route if the route map is satisfied.
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
If a router configured with this command has a route to 0.0.0.0 in the routing table, IS-IS will originate an advertisement for 0.0.0.0 in its LSPs.
Example
In the following configuration, the router is forced to generate a default external route into an IS-IS domain:
router isis! BGP routes will be distributed into IS-ISredistribute bgp 120! access list 2 is applied to outgoing routing updatesdistribute-list 2 outdefault-information originate! access list 2 defined as giving access to network 100.105.0.0access-list 2 permit 100.105.0.0 0.0.255.255Related Commands
default-information originate (OSPF)
To generate a default route into an OSPF routing domain, use the default-information originate router configuration command. To disable this feature, use the no form of this command.
default-information originate [always] [metric metric-value] [metric-type type-value]
{level-1 | level-1-2 | level-2} [route-map map-name]
no default-information originate [always] [metric metric-value] [metric-type type-value]
{level-1 | level-1-2 | level-2} [route-map map-name]Syntax Description
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
Whenever you use the redistribute or the default-information router configuration commands to redistribute routes into an OSPF routing domain, the router automatically becomes an autonomous system boundary router. However, an autonomous system boundary router does not, by default, generate a default route into the OSPF routing domain. The router still needs to have a default route for itself before it generates one, except when you have specified the always keyword.
When you use this command for the OSPF process, the default network must reside in the routing table and you must satisfy the route-map map-name keyword. Use the default-information originate always route-map map-name form of the command when you do not want the dependency on the default network in the routing table.
Example
The following example specifies a metric of 100 for the default route redistributed into the OSPF routing domain and an external metric type of Type 1:
router ospf 109redistribute igrp 108 metric 100 subnetsdefault-information originate metric 100 metric-type 1Related Command
default-metric (BGP, EGP, OSPF, and RIP)
To set default metric values for the BGP, EGP, OSPF, and RIP routing protocols, use this form of the default-metric router configuration command. To return to the default state, use the no form of this command.
default-metric number
no default-metricSyntax Description
Default
Built-in, automatic metric translations, as appropriate for each routing protocol
Command Mode
Router configuration
Usage Guidelines
The default-metric command is used in conjunction with the redistribute router configuration command to cause the current routing protocol to use the same metric value for all redistributed routes. A default metric helps solve the problem of redistributing routes with incompatible metrics. Whenever metrics do not convert, using a default metric provides a reasonable substitute and enables the redistribution to proceed.
In BGP, this sets the multiple exit discriminator (MED) metric. (The name of this metric for BGP Versions 2 and 3 is INTER_AS.)
Example
The following example shows a router in autonomous system 109 using both the RIP and the OSPF routing protocols. The example advertises OSPF-derived routes using the RIP protocol and assigns the OSPF-derived routes a RIP metric of 10.
router ripdefault-metric 10redistribute ospf 109Related Command
default-metric (IGRP and Enhanced IGRP only)
To set metrics for IGRP or Enhanced IGRP, use this form of the default-metric router configuration command. To remove the metric value and restore the default state, use the no form of this command.
default-metric bandwidth delay reliability loading mtu
no default-metric bandwidth delay reliability loading mtuSyntax Description
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
Metric defaults have been carefully set to work for a wide variety of networks. Take great care in changing these values.
Keeping the same metrics is supported only when redistributing from IGRP, Enhanced IGRP, or static routes.
Example
The following example takes redistributed RIP metrics and translates them into IGRP metrics with values as follows: bandwidth = 1000, delay = 100, reliability = 250, loading = 100, and mtu =1500.
router igrp 109network 131.108.0.0redistribute ripdefault-metric 1000 100 250 100 1500Related Command
distance
To define an administrative distance, use the distance router configuration command. To remove a distance definition, use the no form of this command.
distance weight [address mask [access-list-number]] [ip]
no distance weight [address mask [access-list-number]] [ip]Syntax Description
Default
lists default administrative distances.
Table 19-1 Default Administrative Distances
Connected interface
0
Static route
1
External BGP
20
IGRP
100
OSPF
110
IS-IS
115
RIP
120
EGP
140
Internal BGP
200
Unknown
255
Command Mode
Router configuration
Usage Guidelines
Numerically, an administrative distance is an integer between 0 and 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored.
When the optional access list number is used with this command, it is applied when a network is being inserted into the routing table. This behavior allows filtering of networks according to the IP address of the router supplying the routing information. This could be used, as an example, to filter out possibly incorrect routing information from routers not under your administrative control.
The order in which you enter distance commands can affect the assigned administrative distances in unexpected ways (see "Example" for further clarification).
Weight values are also subjective; there is no quantitative method for choosing weight values.
For BGP, the distance command sets the administrative distance of the External BGP route.
The show ip protocols EXEC command displays the default administrative distance for a specified routing process.
Example
In the following example, the router igrp global configuration command sets up IGRP routing in autonomous system number 109. The network router configuration commands specify IGRP routing on networks 192.31.7.0 and 128.88.0.0. The first distance router configuration command sets the default administrative distance to 255, which instructs the router to ignore all routing updates from routers for which an explicit distance has not been set. The second distance command sets the administrative distance for all routers on the Class C network 192.31.7.0 to 90. The third distance command sets the administrative distance for the router with the address 128.88.1.3 to 120.
router igrp 109network 192.31.7.0network 128.88.0.0distance 255distance 90 192.31.7.0 0.0.0.255distance 120 128.88.1.3 0.0.0.0Related Command
distance bgp
To allow the use of external, internal, and local administrative distances that could be a better route to a node, use the distance bgp router configuration command. To return to the default values, use the no form of this command.
distance bgp external-distance internal-distance local-distance
no distance bgpSyntax Description
Default
external-distance: 20
internal-distance: 200
local-distance: 200Command Mode
Router configuration
Usage Guidelines
An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. Numerically, an administrative distance is an integer between 0 and 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored.
Use this command if another protocol is known to be able to provide a better route to a node than was actually learned via external BGP, or if some internal routes should really be preferred by BGP.
Note
Example
In the following example, internal routes are known to be preferable to those learned through the IGP, so the administrative distance values are set accordingly:
router bgp 109network 131.108.0.0neighbor 129.140.6.6 remote-as 123neighbor 128.125.1.1 remote-as 47distance bgp 20 20 200Related Command
distance eigrp
To allow the use of two administrative distances—internal and external—that could be a better route to a node, use the distance eigrp router configuration command. To reset these values to their defaults, use the no form of this command.
distance eigrp internal-distance external-distance
no distance eigrpSyntax Description
Default
internal-distance: 90
external-distance: 170Command Mode
Router configuration
Usage Guidelines
An administrative distance is a rating of the trustworthiness of a routing information source, such as an individual router or a group of routers. Numerically, an administrative distance is an integer between 0 and 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means the routing information source cannot be trusted at all and should be ignored.
Use the distance eigrp command if another protocol is known to be able to provide a better route to a node than was actually learned via external Enhanced IGRP or if some internal routes should really be preferred by Enhanced IGRP.
lists the default administrative distances.
Table 19-2 Default Administrative Distances
To display the default administrative distance for a specified routing process, use the show ip protocols EXEC command.
Example
In the following example, the router eigrp global configuration command sets up Enhanced IGRP routing in autonomous system number 109. The network router configuration commands specify Enhanced IGRP routing on networks 192.31.7.0 and 128.88.0.0. The first distance router configuration command sets the default administrative distance to 255, which instructs the router to ignore all routing updates from routers for which an explicit distance has not been set. The second distance router configuration command sets the administrative distance for all routers on the Class C network 192.31.7.0 to 90. The third distance router configuration command sets the administrative distance for the router with the address 128.88.1.3 to 120.
router eigrp 109network 192.31.7.0network 128.88.0.0distance 255!! use caution when executing the next two commands!!distance 90 192.31.7.0 0.0.0.255distance 120 128.88.1.3 0.0.0.0Related Command
distribute-list in
To filter networks received in updates, use the distribute-list in router configuration command. To change or cancel the filter, use the no form of this command.
distribute-list access-list-number in [interface-name]
no distribute-list access-list-number in [interface-name]Syntax Description
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
This command is not supported in IS-IS.
Example
In the following example, the Enhanced IGRP routing process accepts only two networks—network 0.0.0.0 and network 131.108.0.0:
access-list 1 permit 0.0.0.0access-list 1 permit 131.108.0.0access-list 1 deny 0.0.0.0 255.255.255.255router eigrpnetwork 131.108.0.0distribute-list 1 inRelated Commands
A dagger (†) indicates that the command is documented in another chapter.
access-list (standard) †
access-list (extended) †
distribute-list out
redistributedistribute-list out
To suppress networks from being advertised in updates, use the distribute-list out router configuration command. To cancel this function, use the no form of this command.
distribute-list access-list-number out [interface-name | routing-process |
autonomous-system-number]
no distribute-list access-list-number out [interface-name | routing-process |
autonomous-system-number]Syntax Description
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
When redistributing networks, a routing process name can be specified as an optional trailing argument to the distribute-list command. This causes the access list to be applied to only those routes derived from the specified routing process. After the process-specific access list is applied, any access list specified by a distribute-list command without a process name argument will be applied. Addresses not specified in the distribute-list command will not be advertised in outgoing routing updates.
Note
Examples
The following example would cause only one network to be advertised by a RIP routing process: network 131.108.0.0.
access-list 1 permit 131.108.0.0access-list 1 deny 0.0.0.0 255.255.255.255router ripnetwork 131.108.0.0distribute-list 1 outIn the following example, access list 1 is applied to outgoing routing updates and IS-IS is enabled on Ethernet interface 0. Only network 131.131.101.0 will be advertised in outgoing IS-IS routing updates.
router isisredistribute ospf 109distribute-list 1 outinterface Ethernet 0ip router isisaccess-list 1 permit 131.131.101.0 0.0.0.255Related Commands
A dagger (†) indicates that the command is documented in another chapter.
access-list (standard) †
access-list (extended) †
distribute-list in
redistributedomain-password
To configure the IS-IS routing domain authentication password, use the domain-password router configuration command. To disable a password, use the no form of this command.
domain-password password
no domain-password [password]Syntax Description
Default
No password is specified.
Command Mode
Router configuration
Usage Guidelines
This password is inserted in Level 2 (area router level) link state PDUs (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNP).
Example
The following example assigns an authentication password to the routing domain:
router isisdomain-password flowerRelated Command
ip as-path access-list
To define a BGP-related access list, use the ip as-path access-list global configuration command. To disable use of the access list, use the no form of this command.
ip as-path access-list access-list-number {permit | deny} as-regular-expression
no ip as-path access-list access-list-number {permit | deny} as-regular-expressionSyntax Description
Default
No access lists are defined.
Command Mode
Global configuration
Usage Guidelines
You can specify an access list filter on both inbound and outbound BGP routes. In addition, you can assign weights based on a set of filters. Each filter is an access list based on regular expressions. If the regular expression matches the representation of the autonomous system path of the route as an ASCII string, then the permit or deny condition applies. The autonomous system path does not contain the local autonomous system number. Use the ip as-path access-list global configuration command to define an BGP access list, and the neighbor router configuration command to apply a specific access list.
Example
The following example specifies that the BGP neighbor with IP address 128.125.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 123.
ip as-path access-list 1 deny _123_ip as-path access-list 1 deny ^123$router bgp 109network 131.108.0.0neighbor 129.140.6.6 remote-as 123neighbor 128.125.1.1 remote-as 47neighbor 128.125.1.1 filter-list 1 outRelated Commands
neighbor distribute-list
neighbor filter-listip community-list
To create a community list for BGP and control access to it, use the ip community-list global configuration command. To delete the community list, use the no form of this command.
ip community-list community-list-number {permit | deny} community-number
no ip community-list community-list-numberSyntax Description
community-list-number
Integer 1 through 99 that identifies one or more permit or deny groups of communities.
permit
Permits access for a matching condition.
deny
Denies access for a matching condition.
community-number
Community number configured by a set community command. Valid value is one of the following:
•
•
•
•
Default
Once you permit a value for the community number, the community list defaults to an implicit deny for everything else.
Command Mode
Global configuration
Example
In the following example, the router permits all routes except the routes with the communities 5 and 10 or 10 and 15:
ip community-list 1 deny 5 10ip community-list 1 deny 10 15ip community-list 1 permit internetRelated Command
ip default-network
To select a network as a candidate route for computing the gateway of last resort, use the ip default-network global configuration command. To remove a route, use the no form of this command.
ip default-network network-number
no ip default-network network-numberSyntax Description
Default
If the router has a directly connected interface onto the specified network, the dynamic routing protocols running on that router will generate (or source) a default route. For RIP, this is flagged as the pseudonetwork 0.0.0.0; for IGRP, it is the network itself, flagged as an exterior route.
Command Mode
Global configuration
Usage Guidelines
The router uses both administrative distance and metric information to determine the default route. Multiple ip default-network commands can be given. All candidate default routes, both static (that is, flagged by ip default-network) and dynamic, appear in the routing table preceded by an asterisk.
If the IP routing table indicates that the specified network number is subnetted and a non-zero subnet number is specified, then the system will automatically configure a static summary route. This static summary route is configured instead of a default network. The effect of the static summary route is to cause traffic destined for subnets that are not explicitly listed in the IP routing table to be routed using the specified subnet.
Examples
The following example defines a static route to network 10.0.0.0 as the static default route:
ip route 10.0.0.0 255.0.0.0 131.108.3.4ip default-network 10.0.0.0If the following command was issued on a router not connected to network 129.140.0.0, the router might choose the path to that network as a default route when the network appeared in the routing table:
ip default-network 129.140.0.0Related Command
ip dvmrp accept-filter
To configure an acceptance filter for incoming DVMRP reports, use the ip dvmrp accept-filter interface configuration command. To disable this feature, use the no form of this command.
ip dvmrp accept-filter access-list-number [distance]
no ip dvmrp accept-filter access-list-number [distance]Syntax Description
Default
All destinations are accepted with a distance of 0.
Command Mode
Interface configuration
Usage Guidelines
Any sources that match the access list are stored in the DVMRP routing table with distance.
The distance is used to compare with the same source in the unicast routing table. The route with the lower distance (either the route in the unicast routing table or that in the DVMRP routing table) takes precedence when computing the Reverse Path Forwarding (RPF) interface for a source of a multicast packet.
By default, the administrative distance for DVMRP routes is 0. This means that they always take precedence over unicast routing table routes. If you have two paths to a source, one through unicast routing (using PIM as the multicast routing protocol) and another path using DVMRP (unicast and multicast routing), and if you want to use the PIM path, use the ip dvmrp accept-filter command to increase the administrative distance for DVMRP routes. For example, if the unicast routing protocol is Enhanced IGRP, which has a default administrative distance of 90, you could define and apply the following access list so the RPF interface used to accept multicast packets will be through the Enhanced IGRP/PIM path:
ip dvmrp accept-filter 1 100access-list 1 permit 0.0.0.0 255.255.255.255Example
The following example applies access list 57 to the interface and sets a distance of 4:
access-list 57 permit 131.108.0.0 0.0.255.255access-list 57 permit 198.92.37.0 0.0.0.255access-list 57 deny 0.0.0.0 255.255.255.255ip dvmrp accept-filter 57 4Related Commands
A dagger (†) indicates that the command is documented in another chapter.
distance
ip dvmrp metric
show ip dvmrp route
tunnel mode †ip dvmrp default-information
To advertise network 0.0.0.0 to DVMRP neighbors on an interface, use the ip dvmrp default-information interface configuration command. To prevent the advertisement, use the no form of this command.
ip dvmrp default-information {originate | only}
no ip dvmrp default-information {originate | only}Syntax Description
originate
Other routes more specific than 0.0.0.0 can also be advertised.
only
No DVMRP routes other than 0.0.0.0 are advertised.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command should only be used when the router is a neighbor to mrouted version 3.6 machines. The mrouted protocol is a public domain implementation of DVMRP.
You can use the ip dvmrp metric command with the ip dvmrp default-information command to tailor the metric used when advertising the default route 0.0.0.0. By default, metric 1 is used.
Example
The following example configures the router to advertise network 0.0.0.0, in addition to other networks, to DVMRP neighbors:
ip dvmrp default-information originateRelated Command
ip dvmrp metric
To configure the metric associated with a set of destinations for DVMRP reports, use the ip dvmrp metric interface configuration command. To disable this function, use the no form of this command.
ip dvmrp metric metric [list access-list-number] [protocol process-id] | [dvmrp]
no ip dvmrp metric metric [list access-list-number] [protocol process-id] | [dvmrp]Syntax Description
Default
No metric is preconfigured. Only directly connected subnets and networks are advertised to neighboring DVMRP routers.
Command Mode
Interface configuration
Usage Guidelines
When PIM is configured on an interface and DVMRP neighbors are discovered, the router sends DVMRP report messages for directly connected networks. The ip dvmrp metric command enables DVMRP report messages for multicast destinations that match the access list. Usually, the metric for these routes is 1. Under certain circumstances, it may be desirable to tailor the metric used for various unicast routes.
Use the access-list-number argument in conjunction with the protocol process-id arguments to selectively list the destinations learned from a given routing protocol.
To display DVMRP activity, use the debug ip dvmrp command.
Example
The following example connects a PIM cloud to a DVMRP cloud. Access list 1 permits the sending of DVMRP reports to the DVMRP routers advertising all sources in the 198.92.35.0 network with a metric of 1. Access list 2 permits all other destinations, but the metric of 0 means that no DVMRP reports are sent for these destinations.
access-list 1 permit 198.92.35.0 0.0.0.255access-list 1 deny 0.0.0.0 255.255.255.255access-list 2 permit 0.0.0.0 255.255.255.255interface tunnel 0ip dvmrp metric 1 list 1ip dvmrp metric 0 list 2Related Commands
Two daggers (††) indicate that the command is documented in the Debug Command Reference publication.
debug ip dvmrp ††
ip dvmrp accept-filterip dvmrp metric-offset
To change the metrics of advertised DVMRP routes and thus favor or not favor a certain route, use the ip dvmrp metric-offset interface configuration command. To restore the default values, use the no form of this command.
ip dvmrp metric-offset [in | out] increment
no ip dvmrp metric-offsetSyntax Description
Defaults
If neither in nor out is specified, in is the default.
The default for in is 1.
The default for out is 0.Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.0.
Use this command to influence which routes are used, as you prefer. The DVMRP metric is in hop count.
Example
The following example adds 10 to the incoming DVMRP reports:
ip dvmrp metric-offset 10ip dvmrp reject-non-pruners
To configure the router so that it will not peer with a DVMRP neighbor if that neighbor does not support DVMRP pruning or grafting, use the ip dvmrp reject-non-pruners interface configuration command. To disable the feature, use the no form of this command.
ip dvmrp reject-non-pruners
no ip dvmrp reject-non-prunersSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.0.
By default, the router accepts all DVMRP neighbors as peers, regardless of their DVMRP capability or lack thereof.
Use this command to prevent a router from peering with a DVMRP neighbor if that neighbor does not support DVMRP pruning or grafting. If the router receives a DVMRP Probe or Report message without the Prune-Capable flag set, the router logs a syslog message and discards the message.
Note that this command prevents peering with neighbors only. If there are any non-pruning routers multiple hops away (downstream toward potential receivers) that are not rejected, then a non-pruning DVMRP network might still exist.
Example
The following example configures the router not to peer with DVMRP neighbors that do not support pruning or grafting:
ip dvmrp reject-non-prunersip dvmrp routehog-notification
To change the number of DVMRP routes allowed before a syslog warning message is issued, use the ip dvmrp routehog-notification global configuration command. To restore the default value, use the no form of this command.
ip dvmrp routehog-notification route-count
no ip dvmrp routehog-notificationSyntax Description
Default
10,000 routes
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.2.
This command configures how many DVMRP routes are accepted on each interface within an approximate one-minute interval before a syslog message is issued, warning that there might be a route surge occurring. The warning is typically used to detect quickly when people have misconfigured their routers to inject a large number of routes into the MBONE.
The show ip igmp interface command displays a running count of routes. When the count is exceeded, an "*** ALERT ***" is appended to the line.
Example
The following example lowers the threshold to 8000 routes:
ip dvmrp routehog-notification 8000Related Command
ip dvmrp route-limit
To change the limit on the number of DVMRP routes that can be advertised over an interface enabled to run DVMRP, use the ip dvmrp route-limit global configuration command. To configure no limit, use the no form of this command.
ip dvmrp route-limit count
no ip dvmrp route-limitSyntax Description
Default
7000 routes
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.0.
Interfaces enabled to run DVMRP include a DVMRP tunnel, an interface where a DVMRP neighbor has been discovered, or an interface configured to run ip dvmrp unicast-routing.
The ip dvmrp route-limit command is automatically generated to the configuration file when at least one interface is enabled for multicast routing. This command is necessary to prevent misconfigured ip dvmrp metric commands from causing massive route injection into the multicast backbone (MBONE).
Example
The following example changes the limit to 5000 DVMRP routes allowed to be advertised:
ip dvmrp route-limit 5000Related Command
ip dvmrp unicast-routing
To enable DVMRP unicast routing on an interface, use the ip dvmrp unicast-routing interface configuration command. To disable the feature, use the no form of this command.
ip dvmrp unicast-routing
no ip dvmrp unicast-routingSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
Enabling DVMRP unicast routing means that routes in DVMRP Report messages are cached by the router in a DVMRP routing table. When PIM is running, these routes may get preference over routes in the unicast routing table. This allows PIM to run on the MBONE topology when it is different from the unicast topology.
DVMRP unicast routing can run on all interfaces, including GRE tunnels. On DVMRP tunnels, it runs by virtue of doing DVMRP multicast routing. This command does not enable DVMRP multicast routing among Cisco routers. However, if there is a DVMRP-capable multicast router, the Cisco router will do PIM/DVMRP multicast routing interaction.
Example
The following example enables DVMRP unicast routing:
ip dvmrp unicast-routingRelated Command
ip gdp
To enable GDP routing on an interface, use the ip gdp interface configuration command. To disable GDP routing, use the no form of this command.
ip gdp [priority number | reporttime seconds | holdtime seconds]
no ip gdpSyntax Description
Default
priority: 100
reporttime: 5 seconds for broadcast media; 0 for nonbroadcast media
holdtime: 15 secondsCommand Mode
Interface configuration
Usage Guidelines
When enabled on an interface, GDP updates report the primary and secondary IP addresses of that interface.
Example
In the following example, GDP is enabled on Ethernet interface 1 with a report time of 10 seconds, and priority and hold time set to their defaults (because none are specified):
ip gdp reporttime 10ip hello-interval eigrp
To configure the hello interval for the Enhanced IGRP routing process designated by an autonomous system number, use the ip hello-interval eigrp interface configuration command. To restore the default value, use the no form of this command.
ip hello-interval eigrp autonomous-system-number seconds
no ip hello-interval eigrp autonomous-system-number secondsSyntax Description
Default
For low-speed, NBMA networks: 60 seconds
For all other networks: 5 secondsCommand Mode
Interface configuration
Usage Guidelines
The default of 60 seconds applies only to low speed, nonbroadcast, mutiaccess (NBMA) media. Low speed is considered to be a rate of T1 or slower, as specified with the bandwidth interface configuration command. Note that for the purposes of Enhanced IGRP, Frame Relay and SMDS networks may or may not be considered to be NBMA. These networks are considered NBMA if the interface has not been configured to use physical multicasting; otherwise they are considered not to be NBMA.
Example
The following example sets the hello interval for Ethernet interface 0 to 10 seconds:
interface ethernet 0ip hello-interval eigrp 109 10Related Command
ip hold-time eigrp
To configure the hold time for a particular Enhanced IGRP routing process designated by the autonomous system number, use the ip hold-time eigrp interface configuration command. To restore the default value, use the no form of this command.
ip hold-time eigrp autonomous-system-number seconds
no ip hold-time eigrp autonomous-system-number secondsSyntax Description
Default
For low-speed, NBMA networks: 180 seconds
For all other networks: 15 secondsCommand Mode
Interface configuration
Usage Guidelines
On very congested and large networks, the default hold time might not be sufficient time for all routers to receive hello packets from their neighbors. In this case, you may want to increase the hold time.
We recommend that the hold time be at least three times the hello interval. If a router does not receive a hello packet within the specified hold time, routes through the router are considered unavailable.
Increasing the hold time delays route convergence across the network.
The default of 180 seconds hold time and 60 seconds hello interval apply only to low speed, nonbroadcast, multiaccess (NBMA) media. Low speed is considered to be a rate of T1 or slower, as specified with the bandwidth interface configuration command.
Example
The following example sets the hold time for Ethernet interface 0 to 40 seconds:
interface ethernet 0ip hold-time eigrp 109 40Related Command
ip igmp access-group
To control the multicast groups that hosts on the subnet serviced by an interface can join, use the ip igmp access-group interface configuration command. To disable groups on an interface, use the no form of this command.
ip igmp access-group access-list-number
no ip igmp access-group access-list-numberSyntax Description
Default
All groups are allowed on an interface.
Command Mode
Interface configuration
Example
In the following example, hosts serviced by Ethernet interface 0 can join the group 225.2.2.2 only:
access-list 1 225.2.2.2 0.0.0.0interface ethernet 0ip igmp access-group 1Related Command
ip igmp join-group
To have the router join a multicast group, use the ip igmp join-group interface configuration command. To cancel membership in a multicast group, use the no form of this command.
ip igmp join-group group-address
no ip igmp join-group group-addressSyntax Description
group-address
Address of the multicast group. This is a multicast IP address in four-part dotted notation.
Default
No multicast group memberships are predefined.
Command Mode
Interface configuration
Usage Guidelines
IP packets that are addressed to the group address are passed to the IP client process in the router.
If all the multicast-capable routers that you administer are members of a multicast group, pinging that group causes all routers to respond. This can be a useful administrative and debugging tool.
Another reason to have a router join a multicast group is when other hosts on the network have a bug in IGRP that prevents them from correctly answering IGMP queries. Having the router join the multicast group causes upstream routers to maintain multicast routing table information for that group and keep the paths for that group active.
Example
In the following example, the router joins multicast group 225.2.2.2:
ip igmp join-group 225.2.2.2Related Commands
A dagger (†) indicates that the command is documented in another chapter.
ip igmp access-group
ping (privileged) †
ping (user) †ip igmp query-interval
To configure the frequency at which the router sends IGMP host-query messages, use the ip igmp query-interval interface configuration command. To return to the default frequency, use the no form of this command.
ip igmp query-interval seconds
no ip igmp query-intervalSyntax Description
seconds
Frequency, in seconds, at which to transmit IGMP host-query messages. The can be a number from 0 to 65535. The default is 60 seconds.
Default
60 seconds
Command Mode
Interface configuration
Usage Guidelines
Multicast routers send host membership query messages (referred to as host-query messages) to discover which multicast groups have members on the router's attached networks. Hosts respond with IGMP report messages indicating that they wish to receive multicast packets for specific groups (that is, indicating that the host wants to become a member of the group). Host-query messages are addresses to the all-hosts multicast group, which has the address 224.0.0.1, and have an IP TTL value of 1.
The designated router for a LAN is the only router that sends IGMP host-query messages. The designated router is elected according to the multicast routing protocol that runs on the LAN.
Note
Example
The following example changes the frequency at which the designated router sends IGMP host-query messages to 2 minutes:
interface tunnel 0ip igmp query-interval 120Related Commands
ip pim query-interval
show ip igmp groupsip irdp
To enable ICMP Router Discovery Protocol (IRDP) processing on an interface, use the ip irdp interface configuration command. To disable IRDP routing, use the no form of this command.
ip irdp [multicast | holdtime seconds | maxadvertinterval seconds | minadvertinterval
seconds | preference number | address address [number]]
no ip irdpSyntax Description
Default
Disabled
When enabled, IRDP uses these defaults:
•
•
•
•
Command Mode
Interface configuration
Usage Guidelines
If you change maxadvertinterval, the other two values also change, so it is important to change maxadvertinterval first before changing either holdtime or minadvertinterval.
The ip irdp multicast command allows for compatibility with Sun Microsystems Solaris, which requires IRDP packets to be sent out as multicasts. Many implementations cannot receive these multicasts; ensure end host ability before using this command.
Example
The following example illustrates how to set the various IRDP processes:
! enable irdp on interface Ethernet 0interface ethernet 0 ip irdp ! send IRDP advertisements to the multicast addressip irdp multicast ! increase router preference from 100 to 50ip irdp preference 50 ! set maximum time between advertisements to 400 secsip irdp maxadvertinterval 400 ! set minimum time between advertisements to 100 secsip irdp minadvertinterval 100 ! advertisements are good for 6000 secondsip irdp holdtime 6000 ! proxy-advertise 131.108.14.5 with default router preferenceip irdp address 131.108.14.5 ! proxy-advertise 131.108.14.6 with preference of 50ip irdp address 131.108.14.6 50ip local policy route-map
To identify a route map to use for local policy routing, use the ip local policy route-map global configuration command. To disable local policy routing, use the no form of this command.
ip local policy route-map map-tag
no ip local policy route-map map-tagSyntax Description
map-tag
Name of the route map to use for local policy routing. The name must match a map-tag specified by a route-map command.
Default
Packets that are generated by the router are not policy-routed.
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.0.
Packets that are generated by the router are not normally policy-routed. However, you can use this command to policy-route such packets. You might enable local policy routing if you want packets originated at the router to take a route other than the obvious shortest path.
The ip local policy route-map command identifies a route map to use for local policy routing. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which packets should be policy-routed. The set commands specify the set actions—the particular policy routing actions to perform if the criteria enforced by the match commands are met. The no ip local policy route-map command deletes the reference to the route map and disables local policy routing.
Example
In the following example, packets with a destination IP address matching that allowed by extended access list 131 are sent to the router at IP address 174.21.3.20:
ip local policy route-map xxx!route-map xxxmatch ip address 131set ip next-hop 174.21.3.20Related Commands
match ip address
match length
route-map
set default interface
set interface
set ip default next-hop
set ip next-hop
show ip local policyip mroute
To configure a multicast static route (mroute), use the ip mroute global configuration command. To remove the route, use the no form of this command.
ip mroute source mask [protocol as-number] {rpf-address | type number} [distance]
no ip mroute source mask [protocol as-number] {rpf-address | type number} [distance]Syntax Description
Default
distance: 0
Command Mode
Global configuration
Usage Guidelines
This command allows you to statically configure where multicast sources are located (even though the unicast routing table says something different).
When a source range is specified, the rpf-address applies only to those sources.
Examples
The following example configures all sources via a single interface (in this case, a tunnel):
ip mroute 0.0.0.0 255.255.255.255 tunnel0The following example configures all specific sources within a network number are reachable through 171.68.10.13:
ip mroute 171.69.0.0 255.255.0.0 171.68.10.13The following example causes this multicast static route to take effect if the unicast routes for any given destination go away:
ip mroute 0.0.0.0 255.255.255.255 serial0 200ip mroute-cache
To configure IP multicast fast switching, use the ip mroute-cache interface configuration command. To disable IP multicast fast switching, use the no form of this command.
ip mroute-cache
no ip mroute-cacheSyntax Description
This command has no arguments or keywords.
Default
Enabled
Command Mode
Interface configuration
Usage Guidelines
If fast switching is disabled on an incoming interface for a multicast routing table entry, the packet will be sent at process level for all interfaces in the outgoing interface list.
If fast switching is disabled on an outgoing interface for a multicast routing table entry, the packet is process level switched for that interface, but might be fast-switched for other interfaces in the outgoing interface list.
When fast switching is enabled (like unicast routing), debug messages are not logged. If you want to log debug messages, disable fast switching.
Example
The following example disables IP multicast fast switching on the interface:
no ip mroute-cacheip multicast rate-limit
To control the rate a sender from the source-list can send to a multicast group in the group-list, use the ip multicast rate-limit interface configuration command. To remove the control, use the no form of this command.
ip multicast rate-limit {in | out} [group-list access-list] [source-list access-list] kbps
no multicast rate-limit {in | out} [group-list access-list] [source-list access-list] kbpsSyntax Description
Default
kbps = 0, meaning that there is no limit on the rate traffic is sent.
Command Mode
Interface configuration
Usage Guidelines
If a router receives a packet and in the last second the user has sent over the limit, the packet is dropped; otherwise, it is forwarded.
Example
In the following example, packets to any group from sources in network 171.69.0.0 will have their packets rate-limited to 64 kilobits per second:
interface serial 0ip multicast rate-limit out group-list 1 source-list 2 64access-list 1 permit 0.0.0.0 255.255.255.255access-list 2 permit 171.69.0.0 0.0.255.255ip multicast-routing
To enable IP multicast routing on the router, use the ip multicast-routing global configuration command. To disable IP multicast routing, use the no form of this command.
ip multicast-routing
no ip multicast-routingSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Global configuration
Usage Guidelines
When IP multicast routing is disabled, the router does not forward any multicast packets.
Example
The following example enables IP multicast routing on the router:
ip multicast-routingRelated Command
ip multicast ttl-threshold
To configure the time-to-live (TTL) threshold of packets being forwarded out an interface, use the ip multicast ttl-threshold interface configuration command. To return to the default TTL threshold, use the no form of this command.
ip multicast ttl-threshold ttl
no ip multicast ttl-threshold [ttl]Syntax Description
ttl
Time-to-live value, in hops. It can be a value from 0 to 255. The default value is 0, which means that all multicast packets are forwarded out the interface.
Default
0, which means that all multicast packets are forwarded out the interface.
Command Mode
Interface configuration
Usage Guidelines
Only multicast packets with a TTL value greater than the threshold are forwarded out the interface.
You should configure the TTL threshold only on border routers. Conversely, routers on which you configure a TTL threshold value automatically become border routers.
This command replaces the ip multicast-threshold command, which is obsolete.
Example
In the following example, you set the TTL threshold on a border router to 200, which is a very high value. This means that multicast packets must have a TTL greater than 200 in order to be forwarded out this interface. Multicast applications generally set this value well below 200. Therefore, setting a value of 200 means that no packets will be forwarded out the interface.
interface tunnel 0ip multicast ttl-threshold 200ip ospf authentication-key
To assign a password to be used by neighboring routers that are using OSPF's simple password authentication, use the ip ospf authentication-key interface configuration command. To remove a previously assigned OSPF password, use the no form of this command.
ip ospf authentication-key password
no ip ospf authentication-keySyntax Description
password
Any continuous string of characters that can be entered from the keyboard up to 8 bytes in length.
Default
No password is specified.
Command Mode
Interface configuration
Usage Guidelines
The password created by this command is used as a "key" that is inserted directly into the OSPF header when the router originates routing protocol packets. A separate password can be assigned to each network on a per-interface basis. All neighboring routers on the same network must have the same password to be able to exchange OSPF information.
Note
Example
In the following example, the authentication key is enabled with the string yourpass:
ip ospf authentication-key yourpassRelated Command
ip ospf cost
To explicitly specify the cost of sending a packet on an interface, use the ip ospf cost interface configuration command. To reset the path cost to the default value, use the no form of this command.
ip ospf cost cost
no ip costSyntax Description
cost
Unsigned integer value expressed as the link state metric. It can be a value in the range 1 to 65535.
Default
No default cost is predefined.
Command Mode
Interface configuration
Usage Guidelines
You can set the metric manually using this command. Using the bandwidth command changes the link cost as long as this command is not used.
The link state metric is advertised as the link cost in the router's router link advertisement. We do not support type of service (TOS), so you can assign only one cost per interface.
In general, the path cost is calculated using the following formula:
108 ÷ Bandwidth
Using the above formula, the default path costs were calculated as noted in the following list. If these values do not suit your network, you can use your own method of calculating path costs.
•
•
•
•
•
•
•
•
Example
The following example sets the interface cost value to 65:
ip ospf cost 65ip ospf dead-interval
To set how long a router's Hello packets must not have been seen before its neighbors declare the router down, use the ip ospf dead-interval interface configuration command. To return to the default time, use the no form of this command.
ip ospf dead-interval seconds
no ip ospf dead-intervalSyntax Description
seconds
Unsigned integer that specifies the interval in seconds; the value must be the same for all nodes on the network.
Default
Four times the interval set by the ip ospf hello-interval command
Command Mode
Interface configuration
Usage Guidelines
The interval is advertised in the router's Hello packets. This value must be the same for all routers on a specific network.
Example
The following example sets the OSPF dead interval to 60 seconds:
interface ethernet 1 ip ospf dead-interval 60Related Command
ip ospf hello-interval
To specify the interval between Hello packets that the router sends on the interface, use the ip ospf hello-interval interface configuration command. To return to the default time, use the no form of this command.
ip ospf hello-interval seconds
no ip ospf hello-intervalSyntax Description
seconds
Unsigned integer that specifies the interval in seconds. The value must be the same for all nodes on a specific network.
Default
10 seconds
Command Mode
Interface configuration
Usage Guidelines
This value is advertised in the router's Hello packets. The smaller the Hello interval, the faster topological changes will be detected, but more routing traffic will ensue. This value must be the same for all routers on a specific network.
Example
The following example sets the interval between Hello packets to 15 seconds:
interface ethernet 1ip ospf hello-interval 15Related Command
ip ospf message-digest-key
To enable OSPF MD5 authentication, use the ip ospf message-digest-key interface configuration command. To remove an old MD5 key, use the no form of this command.
ip ospf message-digest-key keyid md5 key
no ip ospf message-digest-key keyidSyntax Description
Default
OSPF MD5 authentication is disabled.
Command Mode
Interface configuration
Usage Guidelines
Usually there is one key per interface, which is used to generate authentication information when sending packets and to authenticate incoming packets. The same key identifier on the neighbor router must have the same key value.
The process of changing keys is as follows. Suppose the current configuration is as follows:
interface ethernet 1ip ospf message-digest-key 100 md5 OLDYou change the configuration to the following:
interface ethernet 1ip ospf message-digest-key 101 md5 NEWThe system assumes its neighbors do not have the new key yet, so it begins a rollover process. It sends multiple copies of the same packet, each authenticated by different keys. In this example, the system sends out two copies of the same packet—the first one authenticated by key 100 and the second one authenticated by key 101.
Rollover allows neighboring routers to continue communication while the network administrator is updating them with the new key. Rollover stops once the local system finds that all its neighbors know the new key. The system detects that a neighbor has the new key when it receives packets from the neighbor authenticated by the new key.
After all neighbors have been updated with the new key, the old key should be removed. In this example, you would enter the following:
interface ethernet 1no ip ospf message-digest-key 100Then, only key 101 is used for authentication on Ethernet interface 1.
We recommend that you not keep more than one key per interface. Every time you add a new key, you should remove the old key to prevent the local system from continuing to communicate with a hostile system that knows the old key. Removing the old key also reduces overhead during rollover.
Example
The following example sets a new key 19 with the password 8ry4222:
interface ethernet 1ip ospf message-digest-key 10 md5 xvv560qleip ospf message-digest-key 19 md5 8ry4222Related Command
area authentication
ip ospf name-lookup
To configure OSPF to look up Domain Name System (DNS) names for use in all OSPF show EXEC command displays, use the ip ospf name-lookup global configuration command. To disable this feature, use the no form of this command.
ip ospf name-lookup
no ip ospf name-lookupSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Global configuration
Usage Guidelines
This feature makes it easier to identify a router because it is displayed by name rather than by its router ID or neighbor ID.
Example
The following example configures OSPF to look up DNS names for use in all OSPF show EXEC command displays:
ip ospf name-lookupSample Display
The following is sample output from the show ip ospf database EXEC command, for example, once you have enabled the DNS name lookup feature.
Router# show ip ospf databaseOSPF Router with id (160.89.41.1) (Autonomous system 109)Router Link States (Area 0.0.0.0)Link ID ADV Router Age Seq# Checksum Link count160.89.41.1 router 381 0x80000003 0x93BB 4160.89.34.2 neon 380 0x80000003 0xD5C8 2Net Link States (Area 0.0.0.0)Link ID ADV Router Age Seq# Checksum160.89.32.1 router 381 0x80000001 0xC117ip ospf network
To configure the OSPF network type to a type other than the default for a given media, use the ip ospf network interface configuration command. To return to the default value, use the no form of this command.
ip ospf network {broadcast | non-broadcast | point-to-multipoint}
no ip ospf networkSyntax Description
broadcast
Sets the network type to broadcast.
non-broadcast
Sets the network type to nonbroadcast.
point-to-multipoint
Sets the network type to point-to-multipoint.
Default
Depends on the network type
Command Mode
Interface configuration
Usage Guidelines
Using this feature, you can configure broadcast networks as nonbroadcast multiaccess networks when, for example, you have routers in your network that do not support multicast addressing. You can also configure nonbroadcast multiaccess networks, such as X.25, Frame Relay, and SMDS, as broadcast networks. This feature saves you from having to configure neighbors.
Configuring nonbroadcast multiaccess networks as either broadcast or nonbroadcast assumes that there are virtual circuits from every router to every router or fully-meshed network. This is not true for some cases, for example, due to cost constraints or when you have only a partially-meshed network. In these cases, you can configure the OSPF network type as a point-to-multipoint network. Routing between two routers that are not directly connected will go through the router that has virtual circuits to both routers. Note that you do not need to configure neighbors when using this feature.
If this command is issued on an interface that does not allow it, it will be ignored.
Example
The following example sets your OSPF network as a broadcast network:
interface serial 0 ip address 160.89.77.17 255.255.255.0ip ospf network broadcastencapsulation frame-relayRelated Commands
A dagger (†) indicates that the command is documented in another chapter.
frame-relay map †
neighbor (OSPF)
x25 map †ip ospf priority
To set the router's priority, which helps determine the designated router for this network, use the ip ospf priority interface configuration command. To return to the default value, use the no form of this command.
ip ospf priority number
no ip ospf prioritySyntax Description
Default
Priority of 1
Command Mode
Interface configuration
Usage Guidelines
When two routers attached to a network both attempt to become the designated router; the one with the higher router priority takes precedence. If there is a tie, the router with the higher router ID takes precedence. A router with a router priority set to zero is ineligible to become the designated router or backup designated router. Router priority is only configured for interfaces to multiaccess networks (in other words, not point-to-point networks).
This priority value is used when you configure OSPF for nonbroadcast networks using the neighbor router configuration command for OSPF.
Example
The following example sets the router priority value to 4:
interface ethernet 0 ip ospf priority 4Related Commands
ip ospf network
neighbor (OSPF)ip ospf retransmit-interval
To specify the time between link state advertisement retransmissions for adjacencies belonging to the interface, use the ip ospf retransmit-interval interface configuration command. To return to the default value, use the no form of this command.
ip ospf retransmit-interval seconds
no ip ospf retransmit-intervalSyntax Description
Default
5 seconds
Command Mode
Interface configuration
Usage Guidelines
When a router sends a link state advertisement (LSA) to its neighbor, it keeps the LSA until it receives back the acknowledgment. If it receives no acknowledgment in seconds, it will retransmit the LSA.
The setting of this parameter should be conservative, or needless retransmission will result. The value should be larger for serial lines and virtual links.
Example
The following example sets the retransmit-interval value to 8 seconds:
interface ethernet 2 ip ospf retransmit-interval 8ip ospf transmit-delay
To set the estimated time it takes to transmit a link state update packet on the interface, use the ip ospf transmit-delay interface configuration command. To return to the default value, use the no form of this command.
ip ospf transmit-delay seconds
no ip ospf transmit-delaySyntax Description
seconds
Time in seconds that it takes to transmit a link state update. It can be an integer in the range is 1 to 65535 seconds. The default is 1 second.
Default
1 second
Command Mode
Interface configuration
Usage Guidelines
Link state advertisements in the update packet must have their age incremented by the amount specified in the seconds argument before transmission. The value assigned should take into account the transmission and propagation delays for the interface.
If the delay is not added before transmission over a link, the time in which the LSA propagates over the link is not considered. This setting has more significance on very low speed links.
Example
The following example sets the retransmit-delay value to 3 seconds:
interface ethernet 0 ip ospf transmit-delay 3ip pim
To enable PIM on an interface, use the ip pim interface configuration command. To disable PIM on the interface, use the no form of this command.
ip pim {dense-mode | sparse-mode}
no ip pim {dense-mode | sparse-mode}Syntax Description
Default
IP multicast routing is disabled on all interfaces.
Command Mode
Interface configuration
Usage Guidelines
Enabling PIM on an interface also enables IGMP operation on that interface. An interface can be configured to be in dense mode or sparse mode. The mode describes how the router populates its multicast routing table and how the router forwards multicast packets it receives from its directly connected LANs. In populating the multicast routing table, dense-mode interfaces are always added to the table. Sparse-mode interfaces are added to the table only when periodic join messages are received from downstream routers or there is a directly connected member on the interface.
Initially, a dense-mode interface forwards multicast packets until the router determines that there are group members or downstream routers, or until a prune message is received from a downstream router. Then, the dense-mode interface will periodically forward multicast packets out the interface until the same conditions occur. Dense mode assumes that there are multicast group members present. Dense-mode routers never send a join message. They do send prune messages as soon as they determine they have no members or downstream PIM routers. A dense-mode interface is subject to multicast flooding by default.
A sparse-mode interface is used for multicast forwarding only if a join message is received from a downstream router or if there are group members directly connected to the interface. Sparse mode assumes that there are no other multicast group members present. When sparse-mode routers want to join the shared path, they periodically send join messages toward the RP. When sparse-mode routers want to join the source path, they periodically send join messages toward the source; they also send periodic prune messages toward to RP to prune the shared path.
Examples
The following commands enables sparse-mode PIM on tunnel interface 0 and sets the address of the RP router to 226.0.0.8:
interface tunnel 0ip pim sparse-modeip pim rp-address 226.0.0.8The following commands enable dense-mode PIM on Ethernet interface 1:
interface ethernet 1ip pim dense-modeRelated Commands
ip multicast-routing
ip pim rp-address
show ip pim interfaceip pim accept-rp
To configure a router to accept Joins or Prunes destined for a specified RP and for a specific list of groups, use the ip pim accept-rp global configuration command. To remove that check, use the no form of this command.
ip pim accept-rp {address | auto-rp} [group-access-list-number]
no ip pim accept-rp {ip-address | auto-rp} [group-access-list-number]Syntax Description
Default
Disabled, so all Join messages and Prune messages are processed.
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.2.
This command causes the router to accept only (*,G) Join messages destined for the specified RP address . Additionally, the group address must be in the range specified by the access list.
When address is one of the system's addresses, the system will be the RP only for the specified group range specified by the access list. When the group address is not in the group range, the RP will not accept Join or Register messages and will respond immediately to Registers with Register-Stop messages.
Example
The following example states that the router will accept Join or Prune messages destined for the RP at address 100.1.1.1 for the multicast group 224.2.2.2:
ip pim accept-rp 100.1.1.1 3access-list 3 permit 224.2.2.2Related Command
access-list (standard)
ip pim nbma-mode
To configure a multiaccess WAN interface to be in nonbroadcast, multiaccess mode, use the ip pim nbma-mode interface configuration command. To disable this feature, use the no form of this command.
ip pim nbma-mode
no pim nbma-modeSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
Use this command on Frame Relay, SMDS, or ATM only, especially when these media do not have native multicast available. Do not use this command on multicast-capable LANs such as Ethernet or FDDI.
When this command is configured, each PIM Join message is kept track of in the outgoing interface list of a multicast routing table entry. Therefore, only PIM WAN neighbors that have joined for the group will get packets sent as data link unicasts. This command should only be used when ip pim sparse-mode is configured on the interface. This command is not recommended for LANs that have natural multicast capabilities.
Example
The following example configures an interface to be in nonbroadcast, multiaccess mode:
ip pim nbma-modeRelated Command
ip pim sparse-mode
ip pim query-interval
To configure the frequency of PIM router-query messages, use the ip pim query-interval interface configuration command. To return to the default interval, use the no form of this command.
ip pim query-interval seconds
no ip pim query-interval [seconds]Syntax Description
seconds
Interval, in seconds, at which periodic PIM router-query messages are sent. It can be a number from 1 to 65535. The default is 30 seconds.
Default
30 seconds
Command Mode
Interface configuration
Usage Guidelines
Routers that are configured for IP multicast send PIM router-query messages to determine which router will be the designated router for each LAN segment (subnet). The designated router is responsible for sending IGMP host-query messages to all hosts on the directly connected LAN. When operating in sparse mode, the designated router is responsible for sending source registration messages to the RP. The designated router is the router with the largest IP address.
Example
The following example changes the PIM router-query message interval to 45 seconds:
interface tunnel 0ip pim query-interval 45Related Command
ip pim rp-address
To configure the address of a PIM rendezvous point (RP) for a particular group, use the ip pim rp-address global configuration command. To remove an RP address, use the no form of this command.
ip pim rp-address ip-address [access-list-number]
no ip pim rp-address ip-address [access-list-number]Syntax Description
Default
No PIM RPs are preconfigured.
Command Mode
Global configuration
Usage Guidelines
You must configure the IP address of RPs in leaf routers only. Leaf routers are those routers that are directly connected either to a multicast group member or to a sender of multicast messages.
The RP address is used by first-hop routers to send register packets on behalf of source multicast hosts to the RP. This address is also used by routers on behalf of multicast hosts that want to become members of a group to send join messages towards the RP. The RP must be a PIM router; however, it does not require any special configuration to recognize that it is the RP. Also, RPs are not members of the multicast group; rather, they serve as a "meeting place" for multicast sources and group members.
Choosing the router that will be an RP requires prior coordination between the people who want to be members of the multicast group. You should examine the length of the paths between members and sources. Remember that most multicast members will eventually want to join to the source tree that is the shortest route between the source and the group member.
You can configure a router to use a single RP for more than one group. The conditions specified by the access list determine which groups the RP can be used for. If no access list is configured, the RP is used for all groups.
A PIM router can use multiple RPs.
First-hop routers for multicast sources send register packets to all configured RPs. First-hop routers for multicast group members send join packets to one RP at a time. Once this router begins receiving multicast packets for the group, it will have joined one RP tree. Because the router does not want to receive multiple copies of the same packet, it joins only one RP tree.
Examples
The following example sets the PIM RP address to 198.92.37.33 for all multicast groups:
ip pim rp-address 198.92.37.33The following example sets the PIM RP address to 147.106.6.22 for the multicast group 225.2.2.2 only:
access list 1 225.2.2.2 0.0.0.0ip pim rp-address 147.106.6.22 1Related Commands
A dagger (†) indicates that the command is documented in another chapter.
access-list (extended) †
access-list (standard) †ip policy route-map
To identify a route map to use for policy routing on an interface, use the ip policy route-map interface configuration command. To disable policy routing on the interface, use the no form of this command.
ip policy route-map map-tag
no ip policy route-map map-tagSyntax Description
map-tag
Name of the route map to use for policy routing. Must match a map-tag specified by a route-map command.
Default
No policy routing occurs on the interface.
Command Mode
Interface configuration
Usage Guidelines
You might enable policy routing if you want your packets to take a route other than the obvious shortest path.
The ip policy route-map command identifies a route map to use for policy routing. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which policy routing is allowed for the interface. The set commands specify the set actions—the particular policy routing actions to perform if the criteria enforced by the match commands are met. The no ip policy route-map command deletes the pointer to the route map.
Example
In the following example, packets with the destination IP address of 174.95.16.18 are sent to the router at IP address 174.21.3.20:
interface serial 0ip policy route-map wethersfield!route-map wethersfieldmatch ip address 174.95.16.18set ip next-hop 174.21.3.20Related Commands
match ip address
match length
route-map
set default interface
set interface
set ip default next-hop
set ip next-hopip route
To establish static routes, use the ip route global configuration command. To remove static routes, use the no form of this command.
ip route network [mask] {address | interface} [distance]
no ip routeSyntax Description
Default
No static routes are established.
Command Mode
Global configuration
Usage Guidelines
A static route is appropriate when the router cannot dynamically build a route to the destination.
If you specify an administrative distance, you are flagging a static route that can be overridden by dynamic information. For example, IGRP-derived routes have a default administrative distance of 100. To have a static route that would be overridden by an IGRP dynamic route, specify an administrative distance greater than 100. Static routes have a default administrative distance of 1.
Static routes that point to an interface will be advertised via RIP, IGRP, and other dynamic routing protocols, regardless of whether redistribute static commands were specified for those routing protocols. This is because static routes that point to an interface are considered in the routing table to be connected and hence lose their static nature. However, if you define a static route to an interface that is not one of the networks defined in a network command, no dynamic routing protocols will advertise the route unless a redistribute static command is specified for these protocols.
Examples
In the following example, an administrative distance of 110 was chosen. In this case, packets for network 10.0.0.0 will be routed through to the router at 131.108.3.4 if dynamic information with administrative distance less than 110 is not available.
ip route 10.0.0.0 255.0.0.0 131.108.3.4 110In the following example, packets for network 131.108.0.0 will be routed to the router at 131.108.6.6:
ip route 131.108.0.0 255.255.0.0 131.108.6.6ip router isis
To configure an IS-IS routing process for IP on an interface, use the ip router isis interface configuration command. To disable IS-IS for IP, use the no form of this command.
ip router isis [tag]
no ip router isis [tag]Syntax Description
Default
No routing processes are specified.
Command Mode
Interface configuration
Example
The following example specifies IS-IS as an IP routing protocol for a process named Finance, and specifies that the Finance process will be routed on interfaces Ethernet 0 and serial 0:
router isis Financeinterface Ethernet 0ip router isis Financeinterface serial 0ip router isis FinanceRelated Command
ip sd listen
To enable the router to listen to session directory advertisements, use the ip sd listen interface configuration command. To disable this feature, use the no form of this command.
ip sd listen
no ip sd listenSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
Session Directory Protocol is a multicast application for creating desktop conferencing sessions. It creates group addresses and allows the user to specify the scope of the group and whether audio, video, or whiteboard applications will be invoked when others open the session.
The ip sd listen command merely enables the router to listen to session directory advertisements. The router joins the default session directory group (group 224.2.127.255) on the interface. Use this command to get contact information.
Example
The following example enables the router to listen to session directory advertisements:
ip sd listenRelated Commands
ip split-horizon
To enable the split-horizon mechanism, use the ip split-horizon interface configuration command. To disable the split-horizon mechanism, use the no form of this command.
ip split-horizon
no ip split-horizonSyntax Description
This command has no arguments or keywords.
Default
Varies with media
Command Mode
Interface configuration
Usage Guidelines
For all interfaces except those for which either Frame Relay or SMDS encapsulation is enabled, the default condition for this command is ip split-horizon; in other words, the split horizon feature is active. If the interface configuration includes either the encapsulation frame-relay or encapsulation smds commands, then the default is for split horizon to be disabled. Split horizon is not disabled by default for interfaces using any of the X.25 encapsulations.
Note
If split horizon has been disabled on an interface and you wish to enable it, use the ip split-horizon command to restore the split horizon mechanism.
Note
Example
The following simple example disables split horizon on a serial link. The serial link is connected to an X.25 network:
interface serial 0encapsulation x25no ip split-horizonRelated Commands
ip split-horizon eigrp
neighborip split-horizon eigrp
To enable Enhanced IGRP split horizon, use the ip split-horizon eigrp interface configuration command. To disable split horizon, use the no form of this command.
ip split-horizon eigrp autonomous-system-number
no ip split-horizon eigrp autonomous-system-numberSyntax Description
Default
Enabled
Command Mode
Interface configuration
Usage Guidelines
For networks that include links over X.25 PSNs, you can use the neighbor router configuration command to defeat the split horizon feature. As an alternative, you can explicitly specify the no ip split-horizon eigrp command in your configuration. However, if you do so, you must similarly disable split horizon for all routers in any relevant multicast groups on that network.
In general, it is recommended that you not change the default state of split horizon unless you are certain that your application requires the change in order to properly advertise routes. Remember that if split horizon is disabled on a serial interface and that interface is attached to a packet-switched network, you must disable split horizon for all routers in any relevant multicast groups on that network.
Example
The following example disables split horizon on a serial link connected to an X.25 network:
interface serial 0encapsulation x25no ip split-horizon eigrpRelated Commands
ip split-horizon
neighborip summary-address eigrp
To configure a summary aggregate address for a specified interface, use the ip summary-address eigrp interface configuration command. To disable a configuration, use the no form of this command.
ip summary-address eigrp autonomous-system-number address mask
no ip summary-address eigrp autonomous-system-number address maskSyntax Description
autonomous-system-number
Autonomous system number.
address
IP summary aggregate address to apply to an interface.
mask
Subnet mask.
Default
No summary aggregate addresses are predefined.
Command Mode
Interface configuration
Usage Guidelines
Enhanced IGRP summary routes are given an administrative distance value of 5. You cannot configure this value.
Example
The following example sets the IP summary aggregate address for Ethernet interface 0:
interface ethernet 0ip summary-address eigrp 109 192.1.0.0 255.255.0.0Related Command
isis circuit-type
To configure the type of adjacency, use the isis circuit-type interface configuration command. To reset the circuit type to Level l and Level 2, use the no form of this command.
isis circuit-type {level-1 | level-1-2 | level-2-only}
no isis circuit-typeSyntax Description
Default
A Level 1 and Level 2 adjacency is established.
Command Mode
Interface configuration
Example
In the following example, a router is configured to require Level 1 adjacency if there is at least one area address in common between this system and its neighbors:
ip router isisinterface serial 0isis circuit-type level-1isis csnp-interval
To configure the IS-IS complete sequence number PDUs (CSNP) interval, use the isis csnp-interval interface configuration command. To restore the default value, use the no form of this command.
isis csnp-interval seconds {level-1 | level-2}
no isis csnp-interval {level-1 | level-2}Syntax Description
Default
10 seconds
Command Mode
Interface configuration
Usage Guidelines
This command only applies for the designated router (DR) for a specified interface. Only DRs send CSNP packets in order to maintain database synchronization. The CSNP interval can be configured independently for Level 1 and Level 2. This feature does not apply to serial point-to-point interfaces. It does apply to WAN connections if the WAN is viewed as a multiaccess meshed network.
Example
In the following example, serial interface 0 is configured for transmitting CSN PDUs every 5 seconds. The router is configured to act as a station router.
interface serial 0isis csnp-interval 5 level-1isis hello-interval
To specify the length of time between Hello packets that the router sends, use the isis hello-interval interface configuration command. To restore the default value, use the no form of this command.
isis hello-interval seconds {level-1 | level-2}
no isis hello-interval {level-1 | level-2}Syntax Description
Default
10 seconds
Command Mode
Interface configuration
Usage Guidelines
The Hello interval can be configured independently for Level 1 and Level 2, except on serial point-to-point interfaces. (Because there is only a single type of Hello packet sent on serial links, it is independent of Level 1 or Level 2.) The level-1 and level-2 keywords are used on X.25, SMDS, and Frame Relay multiaccess networks.
Example
In the following example, serial interface 0 is configured to advertise Hello packets every 5 seconds. The router is configured to act as a station router. This will cause more traffic than configuring a longer interval, but topological changes will be detected faster.
interface serial 0isis hello-interval 5 level-1isis metric
To configure the metric for an interface, use the isis metric interface configuration command. To restore the default metric value, use the no form of this command.
isis metric default-metric [delay-metric [expense-metric [error-metric]]] {level-1 | level-2}
no isis metric {level-1 | level-2}Syntax Description
Default
default-metric = 10
Command Mode
Interface configuration
Usage Guidelines
Specifying the level-1 or level-2 keywords resets the metric only for Level 1 or Level 2 routing, respectively.
Example
In the following example, serial interface 0 is configured for a default link-state metric cost of 15 for Level 1:
interface serial 0isis metric 15 level-1Related Commands
default-information
redistributeisis password
To configure the authentication password for an interface, use the isis password interface configuration command. To disable authentication for IS-IS, use the no form of this command.
isis password password {level-1 | level-2}
no isis password {level-1 | level-2}Syntax Description
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
Different passwords can be assigned for different routing levels using the level-1 and level-2 keyword arguments.
Specifying the level-1 or level-2 keywords disables the password only for Level 1 or Level 2 routing, respectively. If no keyword is specified, the default is level-1.
Example
The following example configures a password for serial interface 0 at Level 1:
interface serial 0isis password frank level-1isis priority
To configure the priority of designated routers, use the isis priority interface configuration command. To reset the default priority, use the no form of this command.
isis priority value {level-1 | level-2}
no isis priority {level-1 | level-2}Syntax Description
Default
Priority of 64
Command Mode
Interface configuration
Usage Guidelines
Priorities can be configured for Level 1 and Level 2 independently. Specifying the level-1 or
level-2 keywords resets priority only for Level 1 or Level 2 routing, respectively.Example
The following example shows Level 1 routing given priority by setting the priority level to 50:
interface serial 0isis priority 50 level-1isis retransmit-interval
To configure the time between retransmission of IS-IS link-state PDU (LSP) retransmission for point-to-point links, use the isis retransmit-interval interface configuration command. To restore the default value, use the no form of this command.
isis retransmit-interval seconds
no isis retransmit-interval secondsSyntax Description
Default
5 seconds
Command Mode
Interface configuration
Usage Guidelines
The setting of the seconds argument should be conservative, or needless retransmission will result. The value should be larger for serial lines and virtual links.
Example
The following example configures serial interface 0 for retransmission of IS-IS LSP every 10 seconds for a large serial line:
interface serial 0isis retransmit-interval 10Related Commands
A dagger (†) indicates that the command is documented in another chapter.
encapsulation ppp †
frame-relay keepalive †
smds dxi †is-type
To configure the IS-IS level at which the router operates, use the is-type router configuration command. To reset the default value, use the no form of this command.
is-type {level-1 | level-1-2 | level-2-only}
no is-type {level-1 | level-1-2 | level-2-only}Syntax Description
level-1
Router acts as a station router.
level-1-2
Router acts as both a station router and an area router.
level-2-only
Router acts as an area router only.
Default
Router acts as both a station router and an area router.
Command Mode
Router configuration
Example
The following example specifies an area router:
router isisis-type level-2-onlymatch as-path
To match a BGP autonomous system path access list, use the match as-path route-map configuration command. To remove a path list entry, the no form of this command.
match as-path path-list-number
no match as-path path-list-numberSyntax Description
Default
No path lists are defined.
Command Mode
Route-map configuration
Usage Guidelines
The values set by the match and set commands override global values. For example, the weights assigned with the match as-path and set weight route-map commands override the weights assigned using the neighbor weight and neighbor filter-list commands.
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route-map section with an explicit match specified.
The implemented weight is based on the first matched autonomous system path.
Example
In the following example, the autonomous system path is set to match BGP autonomous system path access list 20:
route-map igp2bgpmatch as-path 20Related Commands
match community-list
match interface
match ip address
match ip next-hop
match ip route-source
match metric
match route-type
match tag
route-map
set as-path
set automatic-tag
set community
set level
set local-preference
set metric
set metric-type
set next-hop
set origin
set tag
set weightmatch community-list
To match a BGP community, use the match community-list route-map configuration command. To remove the community list entry, use the no form of this command.
match community-list community-list-number [exact]
no match community-list community-list-number [exact]Syntax Description
Default
No community list is defined.
Command Mode
Route-map configuration
Usage Guidelines
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route-map section with an explicit match specified.
Matching based on community list is one of the types of match clauses applicable to BGP.
Examples
In the following example, the routes that match community list 1 will have the weight set to 100. Any route that has community 109 will have the weight set to 100.
ip community-list 1 permit 109!route-map set_weightmatch community-list 1set weight 100In the following example, the routes that match community list 1 will have the weight set to 200. Any route that has community 109 alone will have the weight set to 200.
ip community-list 1 permit 109!route-map set_weightmatch community-list 1 exactset weight 200Related Commands
ip community-list
route-map
set weightmatch interface
To distribute any routes that have their next hop out one of the interfaces specified, use the match interface route-map configuration command. To remove the match interface entry, use the no form of this command.
match interface type number...type number
no match interface type number...type numberSyntax Description
Default
No match interfaces are defined.
Command Mode
Route-map configuration
Usage Guidelines
Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route-map. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route-map section with an explicit match specified.
Example
In the following example, routes that have their next hop out Ethernet interface 0 will be distributed:
route-map namematch interface ethernet 0Related Commands
match as-path
match community-list
match ip address
match ip next-hop
match ip route-source
match metric
match route-type
match tag
route-map
set as-path
set automatic-tag
set community
set level
set local-preference
set metric
set metric-type
set next-hop
set origin
set tag
set weightmatch ip address
To distribute any routes that have a destination network number address that is permitted by a standard access list, or to perform policy routing on packets, use the match ip address route-map configuration command. To remove the match ip address entry, use the no form of this command.
match ip address access-list-number...access-list-number
no match ip address access-list-number...access-list-numberSyntax Description
access-list-number
Number of an access list. It can be an integer from 1 through 99. It can be an extended access list for policy routing.
Default
No access list numbers are specified.
Command Mode
Route-map configuration
Usage Guidelines
Use route maps to redistribute routes or to subject packets to policy routing. Both purposes are described in this section.
•
Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route-map. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The related match commands are listed in the section "Related Commands for Redistribution." The match commands can be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
When you are passing routes through a route map, a route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route-map section with an explicit match specified.
•
Another purpose of route maps is to enable policy routing. Use the ip policy route-map interface configuration command, in addition to the route-map global configuration command, and the match and set route-map configuration commands to define the conditions for policy routing packets. Each route-map command has a list of match and set commands associated with it. The related match and set commands are listed in the section "Related Commands for Policy Routing." The match commands specify the match criteria—the conditions under which policy routing occurs. The set commands specify the set actions—the particular routing actions to perform if the criteria enforced by the match commands are met. You might want to policy route packets based on their source, for example, using an access list.
Examples
In the following example, routes that have addresses specified by access list numbers 5 and 80 will be distributed:
route-map namematch ip address 5 80In the following policy routing example, packets that have addresses specified by access list numbers 6 and 25 will be routed to Ethernet interface 0:
interface serial 0ip policy route-map chicago!route-map chicagomatch ip address 6 25set interface ethernet 0Related Commands for Redistribution
match as-path
match community-list
match interface
match ip next-hop
match ip route-source
match metric
match route-type
match tag
route-map
set as-path
set automatic-tag
set community
set level
set local-preference
set metric
set metric-type
set next-hop
set origin
set tag
set weightRelated Commands for Policy Routing
ip policy route-map
match length
route-map
set default interface
set interface
set ip default next-hop
set ip next-hopmatch ip next-hop
To redistribute any routes that have a next-hop router address passed by one of the access lists specified, use the match ip next-hop route-map configuration command. To remove the next-hop entry, use the no form of this command.
match ip next-hop access-list-number...access-list-number
no match ip next-hop access-list-number...access-list-numberSyntax Description
Default
Routes are distributed freely, without being required to match a next-hop address.
Command Mode
Route-map configuration
Usage Guidelines
Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route-map. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route-map section with an explicit match specified.
Example
In the following example, routes that have a next-hop router address passed by access list 5 or 80 will be distributed:
route-map namematch ip next-hop 5 80Related Commands
match as-path
match community-list
match interface
match ip address
match ip route-source
match metric
match route-type
match tag
route-map
set as-path
set automatic-tag
set community
set level
set local-preference
set metric
set metric-type
set next-hop
set origin
set tag
set weightmatch ip route-source
To redistribute routes that have been advertised by routers at the address specified by the access lists, use the match ip route-source route-map configuration command. To remove the route-source entry, use the no form of this command.
match ip route-source access-list-number...access-list-number
no match ip route-source access-list-number...access-list-numberSyntax Description
Default
No filtering on route source.
Command Mode
Route-map configuration
Usage Guidelines
Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria— the conditions under which redistribution is allowed for the current route-map. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure second route-map section with an explicit match specified.
There are situations in which a route's next hop and source router address are not the same.
Example
In the following example, routes that have been advertised by routers at the addresses specified by access lists 5 and 80 will be distributed:
route-map namematch ip route-source 5 80Related Commands
match as-path
match community-list
match interface
match ip address
match ip next-hop
match metric
match route-type
match tag
route-map
set as-path
set automatic-tag
set community
set level
set local-preference
set metric
set metric-type
set next-hop
set origin
set tag
set weightmatch length
To base policy routing on the Level 3 length of a packet, use the match length route-map configuration command. To remove the entry, use the no form of this command.
match length min max
no match length min maxSyntax Description
Default
No policy routing on the length of a packet.
Command Mode
Route-map configuration
Usage Guidelines
Use the ip policy route-map interface configuration command, the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for policy routing packets. The ip policy route-map command identifies a route map by name. Each route-map has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which policy routing occurs. The set commands specify the set actions—the particular routing actions to perform if the criteria enforced by the match commands are met.
The match route-map configuration command has multiple formats. The match commands can be given in any order, and all match commands must "pass" to cause the packet to be routed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
You might want to base your policy routing on the length of packets so that your interactive traffic and bulk traffic are directed to different routers.
Example
In the following example, packets 3 to 200 bytes long, inclusive, will be routed to FDDI interface 0.
interface serial 0ip policy route-map interactive!route-map interactivematch length 3 200set interface fddi 0Related Commands
ip policy route-map
match ip address
route-map
set default interface
set interface
set ip default next-hop
set ip next-hopmatch metric
To redistribute routes with the metric specified, use the match metric route-map configuration command. To remove the entry, use the no form of this command.
match metric metric-value
no match metric metric-valueSyntax Description
metric-value
Route metric, which can be an IGRP five-part metric. It is a metric value from 0 through 4294967295.
Default
No filtering on a metric value.
Command Mode
Route-map configuration
Usage Guidelines
Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route-map. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure second route-map section with an explicit match specified.
Example
In the following example, routes with the metric 5 will be redistributed.
route-map namematch metric 5Related Commands
match as-path
match community-list
match interface
match ip address
match ip next-hop
match ip route-source
match route-type
match tag
route-map
set as-path
set automatic-tag
set community
set level
set local-preference
set metric
set metric-type
set next-hop
set origin
set tag
set weightmatch route-type
To redistribute routes of the specified type, use the match route-type route-map configuration command. To remove the route-type entry, use the no form of this command.
match route-type {local | internal | external [type-1 | type-2] | level-1 | level-2}
no match route-type {local | internal | external [type-1 | type-2] | level-1 | level-2}Syntax Description
Default
Disabled
Command Mode
Route-map configuration
Usage Guidelines
Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route-map. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure second route-map section with an explicit match specified.
Example
In the following example, internal routes will be redistributed:
route-map namematch route-type internalRelated Commands
match as-path
match community-list
match interface
match ip address
match ip next-hop
match ip route-source
match metric
match tag
route-map
set as-path
set automatic-tag
set community
set level
set local-preference
set metric
set metric-type
set next-hop
set origin
set tag
set weightmatch tag
To redistribute routes in the routing table that match the specified tags, use the match tag route-map configuration command. To remove the tag entry, use the no form of this command.
match tag tag-value...tag-value
no match tag tag-value...tag-valueSyntax Description
Default
No match tag values are defined.
Command Mode
Route-map configuration
Usage Guidelines
Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route-map. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The match commands may be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
A route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure second route-map section with an explicit match specified.
Example
In the following example, routes stored in the routing table with tag 5 will be redistributed:
route-map namematch tag 5Related Commands
match as-path
match community-list
match interface
match ip address
match ip next-hop
match ip route-source
match metric
match route-type
route-map
set as-path
set automatic-tag
set community
set level
set local-preference
set metric
set metric-type
set next-hop
set origin
set tag
set weightmaximum-paths
To control the maximum number of parallel routes an IP routing protocol can support, use the maximum-paths router configuration command. To restore the default value, use the no form of this command.
maximum-paths maximum
no maximum-pathsSyntax Description
maximum
Maximum number of parallel routes an IP routing protocol installs in a routing table, in the range 1 to 6. However, BGP supports only one path.
Defaults
The default for BGP is 1 path. The default for all other IP routing protocols is 4 paths.
Command Mode
Router configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.0.
Example
The following example allows a maximum of 2 paths to a destination:
maximum-paths 2mbranch
To trace a branch of a multicast tree for a specific group, use the mbranch EXEC command.
mbranch {group-address | group-name} branch [ttl]
Syntax Description
Command Mode
EXEC
Usage Guidelines
The mbranch command sends multicast IGMP trace request packets to the specified branch router. It displays information about the branch starting with the local (requesting) router and ending with the branch router. This is considered to be the forward direction.
The information returned shows how a multicast packet sourced by this router will be forwarded by each router on the path to the router with the branch address.
The router with the address branch-address is the only router that responds to the trace request packets. The response is unicast to the source.
It is important to specify a value for the ttl argument if you are tracing through a router on which a multicast threshold has been set with the ip multicast ttl-threshold interface configuration command.
Sample Display
The following is sample output from the mbranch command. This trace is between the same routers as shown in the example for the mbranch command. Note the order of responses. Also note that the outgoing interface list is the same.
PIM2# mbranch 224.0.255.2 198.92.118.2Type escape sequence to abort.Tracing route to group CBONE-WB (224.0.255.2) to 198.92.118.2Response from 10.17.118.10, 76 msec1 PIM9 (10.1.22.9) <- PIM2 (10.1.37.2)Interface list: 131.108.62.0/24 131.108.22.0/24 10.7.0.0/162 PIM-CR (131.108.62.18) <- PIM9 (131.108.62.52)Interface list: 131.108.20.0/24 131.108.53.0/24 131.108.50.0/2410.16.0.0/16 10.17.0.0/163 10.17.118.10 <- 10.17.20.31Interface list: 198.92.118.0/26 198.92.118.192/26The mbranch command is interactive if you specify only the word mbranch. The following output shows sample responses to the system prompts:
Router# mbranchTarget IP group address or name:224.0.255.1Target IP router address or name:sj-eng-f2Ttl [30]:10Source address or name:<CR>Interface:ethernet0Type escape sequence to abort.Tracing route to group cbone-audio.cisco.com (224.0.255.1) to 171.69.4.139Response from sj-eng-f2.cisco.com (171.69.4.139), 4 msec1 sj-eng-cc2.cisco.com (171.69.121.2)<- 0.0.0.0Interface list: 171.69.4.0/242 sj-eng-f2.cisco.com (171.69.4.139)<- sj-eng-cc2.cisco.com (171.69.4.135)Interface list: 171.69.60.128/26describes the fields shown in the first display.
Table 19-3 Mbranch Field Descriptions
Related Commands
ip multicast ttl-threshold
mrbranchmetric holddown
To keep new IGRP routing information from being used for a certain period of time, use the metric holddown router configuration command. To disable this feature, use the no form of this command.
metric holddown
no metric holddownSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
Holddown keeps new routing information from being used for a certain period of time. This can prevent routing loops caused by slow convergence. It is sometimes advantageous to disable holddown to increase the network's ability to quickly respond to topology changes; this command provides this function.
Use the metric holddown command if other routers within the IGRP autonomous system are not configured with no metric holddown. If all routers are not configured the same way, you increase the possibility of routing loops.
Example
The following example disables metric holddown:
router igrp 15network 131.108.0.0network 192.31.7.0no metric holddownRelated Commands
metric maximum-hops
metric weights
timers basic (EGP, RIP, IGRP)metric maximum-hops
To have the IP routing software to advertise as unreachable those routes with a hop count higher than is specified by the command (IGRP only), use the metric maximum-hops router configuration command. To reset the value to the default, use the no form of this command.
metric maximum-hops hops
no metric maximum-hops hopsSyntax Description
hops
Maximum hop count (in decimal). The default value is 100 hops; the maximum number of hops that can be specified is 255.
Default
100 hops
Command Mode
Router configuration
Usage Guidelines
This command provides a safety mechanism that breaks any potential count-to-infinity problems. It causes the IP routing software to advertise as unreachable routes with a hop count greater than the value assigned to the hops argument.
Example
In the following example, a router in autonomous system 71 attached to network 15.0.0.0 wants a maximum hop count of 200, doubling the default. The network administrators decided to do this because they have a complex WAN that can generate a large hop count under normal (nonlooping) operations.
router igrp 71network 15.0.0.0metric maximum-hops 200Related Commands
metric weights
To allow the tuning of the IGRP or Enhanced IGRP metric calculations, use the metric weights router configuration command. To reset the values to their defaults, use the no form of this command.
metric weights tos k1 k2 k3 k4 k5
no metric weightsSyntax Description
tos
Type of service. Currently, it must always be zero.
k1-k5
Constants that convert an IGRP or enhanced IGRP metric vector into a scalar quantity.
Default
tos: 0
k1: 1
k2: 0
k3: 1
k4: 0
k5: 0Command Mode
Router configuration
Usage Guidelines
Use this command to alter the default behavior of IGRP routing and metric computation and allow the tuning of the IGRP metric calculation for a particular type of service (TOS).
If k5 equals 0, the composite IGRP or enhanced IGRP metric is computed according to the following formula:
metric = [k1 * bandwidth + (k2 * bandwidth)/(256 - load) + k3 * delay]If k5 does not equal zero, an additional operation is done:
metric = metric * [k5 / (reliability + k4)]Bandwidth is inverse minimum bandwidth of the path in bits per second scaled by a factor of 2.56 ¥ 1012. The range is from a 1200-bps line to 10 terabits per second.
Delay is in units of 10 microseconds. This gives a range of 10 microseconds to 168 seconds. A delay of all ones indicates that the network is unreachable.
The delay parameter is stored in a 32-bit field, in increments of 39.1 nanoseconds. This gives a range of 1 (39.1 nanoseconds) to hexadecimal FFFFFFFF (decimal 4,294,967,040 nanoseconds). A delay of all ones (that is, a delay of hexadecimal FFFFFFFF) indicates that the network is unreachable.
lists the default values used for several common media.
Table 19-4 Bandwidth Values by Media Type
Reliability is given as a fraction of 255. That is, 255 is 100 percent reliability or a perfectly stable link.
Load is given as a fraction of 255. A load of 255 indicates a completely saturated link.
Example
The following example sets the metric weights to slightly different values than the defaults:
router igrp 109network 131.108.0.0metric weights 0 2 0 2 0 0Related Commands
A dagger (†) indicates that the command is documented in another chapter.
bandwidth †
delay †
metric holddown
metric maximum-hopsmrbranch
To trace a branch of a multicast tree for a group in the reverse direction, use the mrbranch EXEC command.
mrbranch {group-address | group-name} branch-address [ttl]
Syntax Description
Command Mode
EXEC
Usage Guidelines
The mrbranch command sends trace request packets to the specified branch router. Queries are sent recursively to all the routers in the branch. This command displays information about the branch starting with the router farthest away and working towards the requesting router. This is considered to be the reverse direction.
The information returned shows how a multicast packet sourced by this router will be forwarded by each router along the branch.
The router with the address branch-address responds to the trace request packets. The requesting router then sends a query to the router that is the first router's RPF neighbor. Both the request and response packets have unicast addresses.
The number of packets generated by this command is two times the number of routers between the source router and the specified branch router.
Sample Output
The following is sample output from the mrbranch command. This example is between the same router as shown in the mbranch command. Note the order of the responses. Also note that the outgoing interface list is the same.
PIM2# mrbranch 224.0.255.2 10.17.118.10Type escape sequence to abort.Tracing route to group CBONE-WB (224.0.255.2) from 10.17.118.10Response from 10.17.118.10, 68 msec1 10.17.118.10 <- 10.17.20.31Interface list: 198.92.118.0/26 198.92.118.192/26Response from PIM-CR (131.108.62.18), 12 msec1 PIM-CR (131.108.62.18) <- PIM9 (131.108.62.52)Interface list: 131.108.20.0/24 131.108.53.0/24 131.108.50.0/2410.16.0.0/16 10.17.0.0/16Response from PIM9 (131.108.62.52), 8 msec1 PIM9 (131.108.62.52) <- PIM2 (10.1.37.2)Interface list: 131.108.22.0/24 131.108.62.0/24 10.7.0.0/16The mrbranch command is interactive if you specify only the word mrbranch. The following output shows sample responses to the system prompts:
Router# mrbranchTarget IP group address or name:224.0.255.1Target IP router address or name:sj-eng-f2Ttl [30]:10Source address or name:<CR>Interface:ethernet0Type escape sequence to abort.Tracing route to group cbone-audio.cisco.com (224.0.255.1) to 171.69.4.139Response from sj-eng-f2.cisco.com (171.69.4.139), 4 msec1 sj-eng-f2.cisco.com (171.69.4.139)<- sj-eng-cc2.cisco.com (171.69.4.135)Interface list: 171.69.60.128/26Response from sj-eng-f2.cisco.com (171.69.121.2), 4 msec1 sj-eng-cc2.cisco.com (171.69.121.2)<- 0.0.0.0Interface list: 171.69.4.0/24describes the fields shown in the display.
Table 19-5 Mrbranch Field Descriptions
Related Commands
neighbor (EGP, IGRP, RIP)
To define a neighboring router with which to exchange routing information, use this form of the neighbor router configuration command. To remove an entry, use the no form of this command.
neighbor ip-address
no neighbor ip-addressSyntax Description
Default
No neighboring routers are defined.
Command Mode
Router configuration
Usage Guidelines
For exterior routing protocol EGP, this command specifies routing peers. For normally broadcast protocols such as IGRP or RIP, this command permits the point-to-point (nonbroadcast) exchange of routing information. When used in combination with the passive-interface router configuration command, routing information can be exchanged between a subset of routers on a LAN.
Multiple neighbor commands can be used to specify additional neighbors or peers.
OSPF has its own version of the neighbor command. See the neighbor (OSPF) command page in this chapter.
Examples
The following example establishes an EGP neighbor:
autonomous-system 109router egp 110neighbor 131.108.1.1In the following example, IGRP updates are sent to all interfaces on network 131.108.0.0 except interface Ethernet 1. However, in this case a neighbor router configuration command is included. This command permits the sending of routing updates to specific neighbors. One copy of the routing update is generated per neighbor.
router igrp 109network 131.108.0.0passive-interface ethernet 1neighbor 131.108.20.4Related Command
neighbor (OSPF)
To configure OSPF routers interconnecting to nonbroadcast networks, use this form of the neighbor router configuration command. To remove a configuration, use the no form of this command.
neighbor ip-address [priority number] [poll-interval seconds]
no neighbor ip-address [priority number] [poll-interval seconds]Syntax Description
Default
No configuration is specified.
Command Mode
Router configuration
Usage Guidelines
X.25 and Frame Relay provide an optional broadcast capability that can be configured in the map to allow OSPF to run as a broadcast network. At the OSPF level you can configure the router as a broadcast network. See the x25 map and frame-relay map commands in "X.25 Commands" and "Frame Relay Commands" chapters, respectively, for more detail.
One neighbor entry must be included in the router's configuration for each known nonbroadcast network neighbor. The neighbor address has to be on the primary address of the interface.
If a neighboring router has become inactive (Hello packets have not been seen for the Router Dead Interval period), it may still be necessary to send Hello packets to the dead neighbor. These Hello packets will be sent at a reduced rate called Poll Interval.
When the router first starts up, it sends only Hello packets to those routers with non-zero priority, that is, routers which are eligible to become designated routers (DR) and backup designated routers (BDR). After DR and BDR are selected, DR and BDR will then start sending Hello packets to all neighbors in order to form adjacencies.
Example
The following example declares a router at address 131.108.3.4 on a nonbroadcast network, with a priority of 1 and a poll-interval of 180:
router ospf neighbor 131.108.3.4 priority 1 poll-interval 180Related Command
neighbor advertisement-interval
To set the minimum interval between the sending of BGP routing updates, use the neighbor advertisement-interval router configuration command. To remove an entry, use the no form of this command.
neighbor {ip-address | peer-group-name} advertisement-interval seconds
no neighbor {ip-address | peer-group-name} advertisement-interval secondsSyntax Description
ip-address
Neighbor's IP address.
peer-group-name
Name of a BGP peer group.
seconds
Time in seconds. Integer from 0 through 600.
Default
30 seconds for external peers and 5 seconds for internal peers.
Command Mode
Router configuration
Usage Guidelines
If you specify a BGP peer group by using the peer-group-name argument, all of the members of the peer group will inherit the characteristic configued with this command.
Example
In the following example, the minimum time between sending BGP routing updates is set to 10 seconds:
router bgp 5neighbor 4.4.4.4 advertisement-interval 10Related Command
neighbor peer-group (creating)
neighbor any
To control how neighbor entries are added to the routing table for both EGP and BGP, use the neighbor any router configuration command. To remove a configuration, use the no form of this command.
neighbor any [access-list-number]
no neighbor any [access-list-number]Syntax Description
Default
No configuration is specified.
Command Mode
Router configuration
Example
In the following example, only neighbors permitted by access list 1 are allowed to peer with the local router:
access-list 1 permit 10.0.0.0 0.255.255.255! global access list assignmentrouter egp 0neighbor any 1Related Commands
A dagger (†) indicates that the command is documented in another chapter.
access-list (standard) †
neighbor any third-party
router egp 0neighbor any third-party
To configure an EGP process that determines which neighbors are treated as the next hop in EGP advertisements, use the neighbor any third-party router configuration command. To remove a configuration, use the no form of this command.
neighbor any third-party ip-address [internal | external]
no neighbor any third-party ip-address [internal | external]Syntax Description
Default
No EGP process is configured.
Command Mode
Router configuration
Example
The following example specifies the particular neighbors that an EGP process will view as peers:
access-list 2 permit 10.0.0.0 0.255.255.255! global access list assignmentrouter egp 0neighbor any 2neighbor any third-party 10.1.1.1Related Commands
neighbor configure-neighbors
To have the router treat temporary neighbors that have been accepted by a template as if they had been configured manually, use the neighbor configure-neighbors router configuration command. To restore the default, use the no form of this command.
neighbor template-name configure-neighbors
no neighbor template-name configure-neighborsSyntax Description
template-name
User-selectable designation that identifies a particular template. This can be an arbitrary word.
Default
New neighbors are treated as temporary.
Command Mode
Router configuration
Usage Guidelines
Under normal circumstances, neighbors that are allowed to connect to the router because you had configured a template are treated as temporary. When a temporary neighbor disconnects, the local router will not try to actively reestablish a connection with it. In addition, information about temporary neighbors will not show up in the router configuration (write terminal).
When configure-neighbors is enabled on a particular template, any neighbor accepted by that template will be treated as if it had been manually configured. These neighbors will show up in write terminal displays and will be written to the nonvolatile configuration if a write memory command is issued.
Example
In the following example, any BGP speaker matching access list 7 can connect to the router and exchange information. Any neighbor that connects will be treated as if it had been manually configured.
access-list 7 permit 168.89.3.0 0.0.0.255neighbor internal-ethernet neighbor-list 7neighbor internal-ethernet configure-neighborsRelated Command
neighbor default-originate
To allow a BGP speaker (the local router) to send the default route 0.0.0.0 to a neighbor for use as a default route, use the neighbor default-originate router configuration command. To remove the default route, use the no form of this command.
neighbor {ip-address | peer-group-name} default-originate [route-map map-name]
no neighbor {ip-address | peer-group-name} default-originate [route-map map-name]Syntax Description
ip-address
Neighbor's IP address.
peer-group-name
Name of a BGP peer group.
map-name
(Optional) Name of the route map. The route map allows route 0.0.0.0 to be injected conditionally.
Default
No default route is sent to the neighbor.
Command Mode
Router configuration
Usage Guidelines
This command does not require the presence of 0.0.0.0 in the local router. When used with a route map, the default route 0.0.0.0 is injected if the route map contains a match ip address clause and there is a route that matches the IP access list exactly. The route map can contain other match clauses also.
Examples
In the following example, the local router injects route 0.0.0.0 to the neighbor 160.89.2.3 unconditionally:
router bgp 109network 160.89.0.0neighbor 160.89.2.3 remote-as 200neighbor 160.89.2.3 default-originateIn the following example, the local router injects route 0.0.0.0 to the neighbor 160.89.2.3 only if there is a route to 198.92.68.0:
router bgp 109network 160.89.0.0neighbor 160.89.2.3 remote-as 200neighbor 160.89.2.3 default-originate route-map default-map!route-map default-map 10 permitmatch ip address 1!access-list 1 permit 198.92.68.0neighbor distribute-list
To distribute BGP neighbor information as specified in an access list, use the neighbor distribute-list router configuration command. To remove an entry, use the no form of this command.
neighbor {ip-address | peer-group-name} distribute-list access-list-number {in | out}
no neighbor {ip-address | peer-group-name} distribute-list access-list-number {in | out}Syntax Description
Default
No BGP neighbor is specified.
Command Mode
Router configuration
Usage Guidelines
Using distribute lists is one of two ways to filter BGP advertisements. The other way is to use AS-path filters, as with the ip as-path access-list global configuration command and the neighbor filter-list command.
If you specify a BGP peer group by using the peer-group-name argument, all of the members of the peer group will inherit the characteristic configured with this command. Specifying the command with an IP address will override the value inherited from the peer group.
Example
The following example applies list 39 to incoming advertisements to neighbor 120.23.4.1:
router bgp 109network 131.108.0.0neighbor 120.23.4.1 distribute-list 39 inRelated Commands
ip as-path access-list
neighbor filter-list
neighbor peer-group (creating)neighbor ebgp-multihop
To accept and attempt BGP connections to external peers residing on networks that are not directly connected, use the neighbor ebgp-multihop router configuration command. To return to the default, use the no form of this command.
neighbor {ip-address | peer-group-name} ebgp-multihop [ttl]
no neighbor {ip-address | peer-group-name} ebgp-multihopSyntax Description
ip-address
IP address of the BGP-speaking neighbor.
peer-group-name
Name of a BGP peer group.
ttl
Time-to-live in the range 1 to 255 hops.
Default
Only directly connected neighbors are allowed.
Command Mode
Router configuration
Usage Guidelines
This feature should only be used under the guidance of technical support staff.
If you specify a BGP peer group by using the peer-group-name argument, all of the members of the peer group will inherit the characteristic configured with this command.
Example
The following example allows connections to or from neighbor 131.108.1.1, which resides on a network that is not directly connected:
router bgp 109neighbor 131.108.1.1 ebgp-multihopRelated Command
neighbor peer-group (creating)
neighbor filter-list
To set up a BGP filter, use the neighbor filter-list router configuration command. To disable this function, use the no form of this command.
neighbor {ip-address | peer-group-name} filter-list access-list-number {in | out |
weight weight}
no neighbor {ip-address | peer-group-name} filter-list access-list-number {in | out |
weight weight}Syntax Description
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
This command establishes filters on both inbound and outbound BGP routes. Any number of weight filters are allowed on a per-neighbor basis, but only one in or out filter is allowed. The weight of a route affects BGP's route-selection rules.
The implemented weight is based on the first matched autonomous system path. Weights indicated when an autonomous system path is matched override the weights assigned by global neighbor commands. In other words, the weights assigned with the match as-path and set weight route-map commands override the weights assigned using the neighbor weight and neighbor filter-list commands.
See the "Regular Expressions" appendix for information on forming regular expressions.
If you specify a BGP peer group by using the peer-group-name argument, all of the members of the peer group will inherit the characteristic configured with this command. Specifying the command with an IP address will override the value inherited from the peer group.
Example
In the following example, the BGP neighbor with IP address 128.125.1.1 is not sent advertisements about any path through or from the adjacent autonomous system 123:
ip as-path access-list 1 deny _123_ip as-path access-list 1 deny ^123$router bgp 109network 131.108.0.0neighbor 129.140.6.6 remote-as 123neighbor 128.125.1.1 remote-as 47neighbor 128.125.1.1 filter-list 1 outRelated Commands
ip as-path access-list
neighbor distribute-list
neighbor peer-group (creating)
neighbor weightneighbor neighbor-list
To configure BGP to support anonymous neighbor peers by configuring a neighbor template, use the neighbor neighbor-list router configuration command. To delete a template, use the no form of this command.
neighbor template-name neighbor-list access-list-number
no neighbor template-name neighbor-listSyntax Description
template-name
User-selectable designation that identifies a particular template (an arbitrary word).
access-list-number
Number of an access list. It can be a number in the range 1 through 99.
Default
No configuration is defined.
Command Mode
Router configuration
Usage Guidelines
To specify a group of anonymous neighbors, configure a neighbor template rather than specifically configure each neighbor. The template allows you to specify an IP access list which defines remote systems that can establish a BGP connection to the router. External BGP peers must be on a directly connected Ethernet unless they are overridden by the neighbor ebgp-multihop command.
Once you specify a template, you configure the template as if it were a regular neighbor entry, such as setting the protocol version or filter lists, so that anonymous neighbors accepted by the template will receive the settings of the template.
These neighbors accepted by the template appear in the show ip bgp summary and show ip bgp neighbors displays, although they do not appear in the router configuration. When the session is disconnected, all knowledge about the neighbor is discarded and the router will not attempt to actively reestablish a connection.
You can use the neighbor configure-neighbors command to request that the router treat peers learned through a template as if they were manually configured neighbors. These peers will then show up in write terminal displays and can be stored as part of the nonvolatile configuration.
The no neighbor neighbor-list command deletes the template and cause any temporary neighbors accepted by the template to be shut down and removed.
Examples
In the following example, any BGP speaker from 168.89.3.0 can connect to the router and exchange information:
access-list 7 permit 168.89.3.0 0.0.0.255neighbor internal-ethernet neighbor-list 7 neighbor internal-ethernet configure-neighborsIn the following example, any BGP speaker in the connected internet can establish a BGP connection to the local router, and the local router will send them routing information. However, the distribute-list clause instructs the local router to ignore all information these remote BGP speakers send to it.
access-list 9 permit 0.0.0.0 255.255.255.255access-list 10 deny 0.0.0.0 255.255.255.255neighbor route-server-peers neighbor-list 9neighbor route-server-peers distribute-list 10 inRelated Commands
A dagger (†) indicates that the command is documented in another chapter.
access-list (standard) †
neighbor configure-neighbors
neighbor ebgp-multihopneighbor next-hop-self
To disable next-hop processing of BGP updates on the router, use the neighbor next-hop-self router configuration command. To disable this feature, use the no form of this command.
neighbor {ip-address | peer-group-name} next-hop-self
no neighbor {ip-address || peer-group-name} next-hop-selfSyntax Description
Default
Disabled
Command Mode
Router configuration
Usage Guidelines
This command is useful in nonmeshed networks such as Frame Relay or X.25 where BGP neighbors may not have direct access to all other neighbors on the same IP subnet.
If you specify a BGP peer group by using the peer-group-name argument, all of the members of the peer group will inherit the characteristic configured with this command. Specifying the command with an IP address will override the value inherited from the peer group.
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