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Cisco IOS IP Command Reference, Volume 2 of 4: Routing Protocols, Release 12.3 T
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IP Routing Protocol Commands: T Through V
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Introduction
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IP Routing Protocol Commands: A
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IP Routing Protocol Commands: B
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IP Routing Protocols Commands: C through H
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IP Routing Protocols Commands: ignore lsa mospf through ip ospf transmit-delay
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IP Routing Protocol Commands: ip policy route-map through is-type
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IP Routing Protocols Commands: K through M
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IP Routing Protocols Commands: N
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IP Routing Protocols Commands: O through R
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IP Routing Protocols Commands: send-lifetime through set-overload-bit
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IP Routing Protocols Commands: show bgp nsap through show ip bgp update-group
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IP Routing Protocols Commands: show ip cache policy through show ip local policy
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IP Routing Protocol Commands: show ip ospf through synchronization
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Table Of Contents
clear bgp nsap flap-statistics
default-information originate (BGP)
default-information originate (IS-IS)
default-information originate (OSPF)
default-information originate (RIP)
capability lls
To enable the use of the Link-Local Signalling (LLS) data block in originated OSPF packets and reenable OSPF nonstop forwarding (NSF) awareness, use the capability lls command in router configuration mode. To disable LLS and OSPF NSF awareness, use the no form of this command.
capability lls
no capability lls
Syntax Description
This command has no arguments or keywords.
Defaults
LLS is enabled.
Command Modes
Router configuration
Command History
Usage Guidelines
You might want to disable NSF awareness by disabling the use of the LLS data block in originated OSPF packets. You might want to disable NSF awareness if the router has no applications using LLS.
If NSF is configured and you try to disable LLS, you will receive the error message, "OSPF Non-Stop Forwarding (NSF) must be disabled first."
If LLS is disabled and you try to configure NSF, you will receive the error message, "OSPF Link-Local Signaling (LLS) capability must be enabled first."
Examples
The following example disables LLS support and OSPF NSF awareness:
router ospf 2no capability llscapability transit
To reenable Open Shortest Path First (OSPF) area capability transit after it has been disabled, use the capability transit command in router configuration mode. To disable OSPF area capability transit on all areas for a router process, use the no form of this command.
capability transit
no capability transit
Syntax Description
This command has no arguments or keywords.
Defaults
OSPF area transit capability is enabled.
Command Modes
Router configuration
Command History
Usage Guidelines
OSPF area capability transit is enabled by default, allowing the OSPF Area Border Router to install better-cost routes to the backbone area through the transit area instead of the virtual links. If you want to retain a traffic pattern through the virtual-link path, you can disable capability transit by entering the no capability transit command. If paths through the transit area are discovered, they are most likely to be more optimal paths, or at least equal to, the virtual-link path. To reenable capability transit, enter the capability transit command.
If you need to verify whether OSPF area transit capability is enabled for a specific routing process, enter the show ip ospf command.
Examples
The following example shows how to disable OSPF area transit capability on all areas for a router process named ospf 1. A show ip ospf command is issued first to display the current areas that have area transit capability enabled. The no capability transit command is then entered to disable OSPF area transit capability on all areas for the router process ospf 1.
Router# show ip ospfRouting Process "ospf 1" with ID 10.1.1.1Supports only single TOS(TOS0) routesSupports opaque LSASupports Link-local Signaling (LLS)!Supports area transit capabilityIt is an area border routerInitial SPF schedule delay 5000 msecsMinimum hold time between two consecutive SPFs 10000 msecsMaximum wait time between two consecutive SPFs 10000 msecsMinimum LSA interval 5 secs. Minimum LSA arrival 1 secsLSA group pacing timer 240 secsInterface flood pacing timer 33 msecsRetransmission pacing timer 66 msecsNumber of external LSA 8. Checksum Sum 0x02853FNumber of opaque AS LSA 0. Checksum Sum 0x000000Number of DCbitless external and opaque AS LSA 0Number of DoNotAge external and opaque AS LSA 0Number of areas in this router is 2. 2 normal 0 stub 0 nssa!Number of areas transit capable is 1External flood list length 0Area BACKBONE(0)Number of interfaces in this area is 3Area has no authenticationSPF algorithm last executed 00:02:21.524 agoSPF algorithm executed 11 timesArea ranges areNumber of LSA 49. Checksum Sum 0x19B5FANumber of opaque link LSA 0. Checksum Sum 0x000000Number of DCbitless LSA 0Number of indication LSA 0Number of DoNotAge LSA 38Flood list length 0Area 1Number of interfaces in this area is 3!This area has transit capability: Virtual Link EndpointArea has no authenticationSPF algorithm last executed 00:02:36.544 agoSPF algorithm executed 9 timesArea ranges areNumber of LSA 42. Checksum Sum 0x1756D5Number of opaque link LSA 0. Checksum Sum 0x000000Number of DCbitless LSA 0Number of indication LSA 0Number of DoNotAge LSA 0Flood list length 0Router(config) router ospf 1Router(router-config) no capability transitRelated Commands
capability vrf-lite
To suppress the Provider Edge (PE) specific checks on a router when the OSPF process is associated with the VRF, use the capability vrf-lite command in router configuration mode. To restore the checks, use the no form of this command.
capability vrf-lite
no capability vrf-lite
Syntax Description
This command has no arguments or keywords.
Defaults
Disabled. PE specific checks are performed if the process is associated with VRF command modes.
Command Modes
Router configuration
Command History
Usage Guidelines
This command works only if the OSPF process is associated with the VRF.
When the OSPF process is associated with the VRF, several checks are performed when link-state advertisements (LSAs) are received. PE checks are needed to prevent loops when the PE is performing a mutual redistribution between OSPF and BGP interfaces.
In some situations, performing PE checks might not be desirable. The concept of VRFs can be used on a router that is not a PE router (that is, a router that is not running BGP). With the capability vrf-lite command, the checks can be turned off to allow correct population of the VRF routing table with routes to IP prefixes.
Examples
This example shows a router configured with multi-VRF.
router ospf 100 vrf grccapability vrf-liteclear bgp nsap
To clear and then reset Connectionless Network Service (CLNS) network service access point (NSAP) Border Gateway Protocol (BGP) sessions, use the clear bgp nsap command in privileged EXEC mode.
clear bgp nsap {* | as-number | ip-address} [soft] [in | out]
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear bgp nsap command is similar to the clear ip bgp command, except that it is NSAP address family-specific.
Use of the clear bgp nsap command allows a reset of the neighbor sessions with varying degrees of severity, depending on the specified keywords and arguments.
Use the * keyword to reset all neighbor sessions. The software will clear and then reset the neighbor connections. Use this form of the command in the following situations:
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BGP timer specification change
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Use the soft out keywords to clear and reset only the outbound neighbor connections. Inbound neighbor sessions will not be reset. Use this form of the command in the following situations:
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Use the in keyword to clear only the inbound neighbor connections. Outbound neighbor sessions will not be reset. Use this form of the command in the following situations:
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Examples
In the following example, the inbound session with the neighbor 172.20.16.6 is cleared without the outbound session being reset:
Router# clear bgp nsap 172.20.16.6 inIn the following example, a soft clear is applied to outbound sessions with the neighbors in autonomous system 65000 without the inbound session being reset:
Router# clear bgp nsap 65000 soft outRelated Commands
show bgp nsap
Displays entries in the BGP routing table for the NSAP address family.
clear bgp nsap dampening
To clear Border Gateway Protocol (BGP) route dampening information for the network service access point (NSAP) address family and unsuppress the suppressed routes, use the clear bgp nsap dampening command in privileged EXEC mode.
clear bgp nsap dampening [nsap-prefix]
Syntax Description
nsap-prefix
(Optional) NSAP prefix about which to clear dampening information. This argument can be up to 20 octets long.
Defaults
When the nsap-prefix argument is not specified, the clear bgp nsap dampening command clears route dampening information for the entire BGP routing table for the NSAP address family.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear bgp nsap dampening command is similar to the clear ip bgp dampening command, except that it is specific to the NSAP address family.
Examples
In the following example, route dampening information is cleared for the route to NSAP prefix 49.6001 and locally suppressed routes are unsuppressed:
Router# clear bgp nsap dampening 49.6001Related Commands
bgp dampening
Enables BGP route dampening or changes various BGP route dampening factors.
show bgp nsap dampened-paths
Displays BGP dampened routes for the NSAP address family.
clear bgp nsap external
To clear all external BGP (eBGP) peers for the network service access point (NSAP) address family, use the clear bgp nsap external command in privileged EXEC mode.
clear bgp nsap external [soft] [in | out]
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear bgp nsap external command is similar to the clear ip bgp external command, except that it is specific to the NSAP address family.
Examples
In the following example, the inbound sessions with external BGP peers are cleared without the outbound sessions being reset:
Router# clear bgp nsap external soft inRelated Commands
clear bgp nsap flap-statistics
To clear Border Gateway Protocol (BGP) flap statistics for the network service access point (NSAP) address family, use the clear bgp nsap flap-statistics command in privileged EXEC mode.
clear bgp nsap flap-statistics [nsap-prefix] [regexp regexp | filter-list access-list-number]
Syntax Description
Defaults
No statistics are cleared.
If no arguments or keywords are specified, the software clears flap statistics for all routes.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear bgp nsap flap-statistics command is similar to the clear ip bgp flap-statistics command, except that it is specific to the NSAP address family.
The flap statistics for a route are also cleared when an NSAP BGP peer is reset. Although the reset withdraws the route, no penalty is applied in this instance even though route flap dampening is enabled.
Examples
In the following example, all of the flap statistics for paths that pass access list 3 are cleared:
Router# clear bgp nsap flap-statistics filter-list 3Related Commands
bgp dampening
Enables BGP route dampening or changes various BGP route dampening factors.
show bgp nsap flap-statistics
Displays BGP flap statistics for the NSAP address family.
clear bgp nsap peer-group
To clear the Border Gateway Protocol (BGP) TCP connections to all members of a BGP peer group for the network service access point (NSAP) address family, use the clear bgp nsap peer-group command in privileged EXEC mode.
clear bgp nsap peer-group peer-group-name
Syntax Description
Defaults
No BGP TCP connections are cleared.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear bgp nsap peer-group command is similar to the clear ip bgp peer-group command, except that it is specific to the NSAP address family.
Examples
In the following example, the BGP TCP connections are cleared for all members of the NSAP BGP peer group named internal:
Router# clear bgp nsap peer-group internalRelated Commands
neighbor peer-group (assigning members)
Configures a BGP neighbor to be a member of a peer group.
clear ip bgp
To reset Border Gateway Protocol (BGP) connections using hard or soft reconfiguration, use the clear ip bgp command in privileged EXEC mode.
clear ip bgp {* | all | ipv4 {multicast | unicast} as-number | ipv6 {multicast | unicast} as-number | vpnv4 {unicast} as-number | as-number | neighbor-address} [soft [in | out]]
Syntax Description
Defaults
No default behavior or values
Command Modes
Privileged EXEC
Command History
10.0
This command was introduced.
12.0(6)T
The dynamic inbound soft reset capability was added.
12.0(2)S
The dynamic inbound soft reset capability was added.
Usage Guidelines
The clear ip bgp command can be used to initiate a hard reset or soft reconfiguration. A hard reset tears down and rebuilds the specified peering sessions and rebuilds the BGP routing tables. A soft reconfiguration uses stored prefix information to reconfigure and activate BGP routing tables without tearing down existing peering sessions. Soft reconfiguration uses stored update information, at the cost of additional memory for storing the updates, to allow you to apply new BGP policy without disrupting the network. Soft reconfiguration can be configured for inbound or outbound sessions.
Generating Updates From Stored Information
To generate new inbound updates from stored update information (rather than dynamically) without resetting the BGP session, you must preconfigure the local BGP router using the neighbor soft-reconfiguration inbound command. This preconfiguration causes the software to store all received updates without modification regardless of whether an update is accepted by the inbound policy. Storing updates is memory intensive and should be avoided if possible.
Outbound BGP soft configuration has no memory overhead and does not require any preconfiguration. You can trigger an outbound reconfiguration on the other side of the BGP session to make the new inbound policy take effect.
Use this command whenever any of the following changes occur:
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Dynamic Inbound Soft Reset
The route refresh capability, as defined in RFC-2918, allows the local router to reset inbound routing tables dynamically by exchanging route refresh requests to supporting peers. The route refresh capability does not store update information locally for non-disruptive policy changes. It instead relies on dynamic exchange with supporting peers. Route refresh is advertised through BGP capability negotiation. All BGP routers must support the route refresh capability.
To determine if a BGP router supports this capability, use the show ip bgp neighbors command. The following message is displayed in the output when the router supports the route refresh capability:
Received route refresh capability from peer.If all BGP routers support the route refresh capability, use the clear ip bgp {* | address | peer-group-name} in command. You need not use the soft keyword, because soft reset is automatically assumed when the route refresh capability is supported.
Note
Examples
In the following example, a soft reconfiguration is initiated for the inbound session with the neighbor 10.108.1.1, and the outbound session is unaffected:
Router# clear ip bgp 10.100.0.1 soft inIn the following example, a hard reset is initiated for sessions with all routers in the peer group named CORP:
Router# clear ip bgp CORPRelated Commands
neighbor soft-reconfiguration
Configures the Cisco IOS software to start storing updates.
show ip bgp
Displays entries in the BGP routing table.
clear ip bgp dampening
To clear BGP route dampening information and to unsuppress suppressed routes, use the clear ip bgp dampening command in privileged EXEC mode.
clear ip bgp [ipv4 {multicast | unicast} | ipv6 {multicast | unicast} | vpnv4 {unicast}] dampening [neighbor-address] [ipv4-mask]
Syntax Description
Defaults
When entering the neighbor-address argument, you will be prompted for an IPv4 address if no address family keyword is specified.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear ip bgp dampening is used to cleared stored route dampening information. If no keywords or arguments are entered, route dampening information for the entire routing table is cleared.
Examples
The following example clears route dampening information for VPNv4 address family prefixes from network 192.168.10.0/24, and unsuppresses its suppressed routes.
Router# clear ip bgp vpnv4 unicast dampening 192.168.10.0 255.255.255.0Related Commands
clear ip bgp external
To clear external Border Gateway Protocol (eBGP) peering sessions, use the clear ip bgp external command in privileged EXEC mode.
clear ip bgp external [ipv4 {multicast | unicast} | ipv6 {multicast | unicast} | vpnv4 {unicast}] [vrf name] [soft [in | out]]
Syntax Description
Defaults
No default behavior or values
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear ip bgp external command is used to reset eBGP peering sessions. The usage guidelines for the clear ip bgp command apply to this command.
Examples
In the following example, a soft reconfiguration is configured for all inbound eBGP peering sessions:
Router# clear ip bgp external soft inIn the following example, all outbound address family IPv4 multicast eBGP peering sessions are cleared:
Router# clear ip bgp external ipv4 multicast outRelated Commands
clear ip bgp flap-statistics
To clear BGP route dampening flap statistics, use the clear ip bgp flap-statistics command in privileged EXEC mode.
clear ip bgp flap-statistics [neighbor-address [ipv4-mask]] [regexp regexp | filter-list extcom-number]
clear ip bgp [neighbor-address] [ipv4 {multicast | unicast} | ipv6 {multicast | unicast} | vpnv4 {unicast}] flap-statistics
Syntax Description
Defaults
When entering the neighbor-address argument, you will be prompted for an IPv4 address if no address family keyword is specified.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear ip bgp flap-statistics command is used to clear the accumulated penalty for routes that are received on a router that has BGP dampening enabled. If no arguments or keywords are specified, flap statistics are cleared for all routes. Flap statistics are also cleared when the peer is stable for the half-life time period.
Examples
In the following example, all of the flap statistics are cleared for paths that pass filter list 3:
Router# clear ip bgp flap-statistics filter-list 3Related Commands
clear ip bgp in prefix-filter
To initiate an inbound soft reset to clear a BGP outbound route filter (ORF), use the clear ip bgp in prefix-filter command in privileged EXEC mode.
clear ip bgp ip-address | peer-group-name in prefix filter
Syntax Description
Defaults
The prefix-filter keyword will be ignored and a normal inbound route refresh or soft reset will be performed if ORF capabilities have not been enabled locally or received from the sending BGP peer.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear ip bgp in prefix-filter command is used to clear the existing ORF prefix list to trigger a new route refresh or soft reconfiguration, which updates the ORF prefix list. If the clear ip bgp in command is entered without the prefix-filter keyword, a normal route refresh is performed. This command should be used when inbound routing policy changes (other than a prefix list filter) occur, such as a route map change.
Examples
In the following example, an inbound soft reset is initiated to clear the BGP ORF received from the 192.168.0.1 neighbor:
Router# clear ip bgp 192.168.0.1 in prefix-filterRelated Commands
clear ip bgp peer-group
To clear all the members of a BGP peer group, use the clear ip bgp peer-group command in privileged EXEC mode.
clear ip bgp [all | ipv4 {multicast | unicast} | ipv6 {multicast | unicast} | vpnv4 {unicast}] peer-group name [soft [in | out]]
Syntax Description
Defaults
No default behavior or values
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear ip bgp peer-group command is used to reset peering sessions for BGP peer groups. The usage guidelines for the clear ip bgp command apply to this command.
Examples
In the following example, all members of the BGP peer group named INTERNAL are cleared:
Router# clear ip bgp peer-group INTERNALRelated Commands
clear ip bgp
Resets a BGP connection or session.
neighbor peer-group (assigning members)
Configures a BGP neighbor to be a member of a peer group.
clear ip bgp table-map
To refresh table-map configuration information in the Border Gateway Protocol (BGP) routing table, use the clear ip bgp table-map command in privileged EXEC mode.
clear ip bgp [ipv4 {multicast | unicast} | ipv6 {multicast | unicast} | vpnv4 {unicast}] table-map
Syntax Description
Defaults
No default behavior or values
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear ip bgp table-map command is used to clear or refresh table-map configuration information in BGP routing tables. This command can be used to clear traffic-index information configured with the BGP Policy Accounting feature.
Examples
In the following example, a table map is configured and a traffic index is set. The new policy is applied after the clear ip bgp table-map command is entered.
Router(config)# route-map SET_BUCKET permit 10Router(config-route-map)# match community 1Router(config-route-map)# set traffic-index 2Router(config-route-map)# exitRouter(config)# router bgp 50000Router(config-router)# address-family ipv4Router(config-router-af)# table-map SET_BUCKETRouter(config-router-af)# endRouter# clear ip bgp table-mapRelated Commands
clear ip bgp update-group
T o clear Border Gateway Protocol (BGP) update-group member sessions, use the clear ip bgp update-group command in privileged EXEC mode.
clear ip bgp [all | ipv4 {multicast | unicast} | ipv6 {multicast | unicast}] update-group [index-group | neighbor-address]
Syntax Description
Defaults
No default behavior or values
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear ip bgp update-group command is used to clear BGP update group member sessions. If no keywords or arguments are specified, entering this command will recalculate all update groups. Specific index numbers for update groups and information about update-group membership is displayed in the output of the show ip bgp update-group and debug ip bgp groups commands.
When a change to outbound policy occurs, the BGP routing process will automatically recalculate update-group memberships and apply changes by triggering an outbound soft reset after a 3-minute timer expires. This behavior is designed to provide the network operator with time to change the configuration before the soft reset is initiated. You can immediately initiate the outbound soft reset before the timer expires by entering the clear ip bgp ip-address soft out command or immediately initiate a hard reset by entering the clear ip bgp ip-address command.
Examples
In the following example, the membership of the 10.0.0.1 peer is cleared from an update group:
Router# clear ip bgp update-group 10.0.0.1In the following example, update-group information for all peers in the index 1 update group is cleared:
Router# clear ip bgp update-group 1Related Commands
clear ip eigrp neighbors
To delete entries from the neighbor table, use the clear ip eigrp neighbors command in EXEC mode.
clear ip eigrp neighbors [ip-address | interface-type interface-number]
Syntax Description
Command Modes
EXEC
Command History
Examples
The following example removes the neighbor whose address is 172.16.8.3:
Router# clear ip eigrp neighbors 172.16.8.3Related Commands
show ip eigrp interfaces
Displays information about interfaces configured for EIGRP.
clear ip eigrp vrf neighbor
To clear neighbor entries of the specified Enhanced Interior Gateway Routing Protocol (EIGRP) virtual routing and forwarding instance (VRF) from the Routing Information Base (RIB), use the clear ip eigrp vrf command in privileged EXEC mode.
clear ip eigrp vrf {vrf-name as-number} neighbor [interface-number]
Syntax Description
Command Modes
Privileged EXEC
Command History
12.0(22)S
This command was introduced.
12.2(15)T
This command was integrated into 12.2(15)T.
Examples
The following example clears EIGRP neighbors reached through the VRF named VRF-RED in autonomous system 101:
clear ip eigrp vrf VRF-RED 101 neighborThe following example clears EIGRP neighbors reached through the VRF named VRF-GREEN in autonomous-system 101 learned through Ethernet interface 0/0:
clear ip eigrp vrf VRF-RED 101 neighbor ethernet 0/0Related Commands
clear ip ospf
To clear redistribution based on the OSPF routing process ID, use the clear ip ospf command in privileged EXEC mode.
clear ip ospf [pid] {process | redistribution | counters [neighbor [neighbor-interface] [neighbor-id]]}
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
Use the pid argument to clear only one OSPF process. If the pid argument is not specified, all OSPF processes are cleared.
Examples
The following example clears all OSPF processes:
clear ip ospf processclear ip ospf traffic
To clear Open Shortest Path First (OSPF) traffic statistics, use the clear ip ospf traffic command in user EXEC or privileged EXEC mode.
clear ip ospf [process-id] traffic [interface-type interface-number]
Syntax Description
Command Modes
User EXEC
Privileged EXECCommand History
12.3(11)T
This command was introduced.
12.0(28)S
This command was integrated into Cisco IOS Release 12.0(28)S.
Examples
The following example clears OSPF traffic statistics for the OSPF process 100:
Router# clear ip ospf 100 trafficRelated Commands
clear ip prefix-list
To reset IP prefix-list counters, use the clear ip prefix-list command in privileged EXEC mode.
clear ip prefix-list [[prefix-list-name] [network/length]]
Syntax Description
Defaults
No default behavior or values
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The clear ip prefix-list command is used to clear prefix-list hit counters. The hit count is a value indicating the number of matches to a specific prefix list entry.
Examples
In the following example, the prefix-list counters are cleared for the prefix list named FIRST_LIST that matches the 10.0.0.0/8 prefix:
Router# clear ip prefix-list FIRST_LIST 10.0.0.0/8Related Commands
clear isis lsp-full
To clear the LSPFULL state, use the clear isis lsp-full command in privileged EXEC mode.
clear isis lsp-full
Syntax Description
This command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
If the link-state PDU (LSP) becomes full because too many routes are redistributed, use the clear isis lsp-full command to clear the state after the problem has been resolved.
Examples
This example clears the LSPFULL state:
Router# clear isis lsp-fullRelated Commands
lsp-full suppress
Controls which routes are suppressed when the link-state PDU becomes full.
clear isis rib redistribution
To clear some or all prefixes in the Intermediate System-to-Intermediate System (IS-IS) redistribution cache, use the clear isis rib redistribution command in privileged EXEC mode.
clear isis rib redistribution [level-1 | level-2] [network-prefix] [network-mask]
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
We recommend that you use this command in a troubleshooting situation only when a Cisco Technical Assistance Center representative requests you to do so following a software error.
Examples
The following example clears the network prefix 10.1.0.0 from the IP local redistribution cache:
Router# clear isis rib redistribution 10.1.0.0 255.255.0.0Related Commands
debug isis rib redistribution
Debugs the local redistribution cache event.
show isis rib redistribution
Displays the prefixes in the IS-IS redistribution cache.
compatible rfc1583
To restore the method used to calculate summary route costs per RFC 1583, use the compatible rfc1583 command in router configuration mode. To disable RFC 1583 compatibility, use the no form of this command.
compatible rfc1583
no compatible rfc1583
Syntax Description
This command has no arguments or keywords.
Defaults
Compatible with RFC 1583.
Command Modes
Router configuration
Command History
Usage Guidelines
This command is backward compatible with Cisco IOS Release 12.0.
To minimize the chance of routing loops, all OSPF routers in an OSPF routing domain should have RFC compatibility set identically.
Because of the introduction of RFC 2328, OSPF Version 2, the method used to calculate summary route costs has changed. Use the no compatible rfc1583 command to enable the calculation method used per RFC 2328.
Examples
The following example specifies that the router process is compatible with RFC 1583:
router ospf 1compatible rfc1583!continue
To configure a route-map to go to a route-map entry with a higher sequence number, use the continue command in route-map configuration mode. To disable a continue clause within a route-map, use the no form of this command.
continue sequence-number
no continue
Syntax Description
Defaults
If the sequence number argument is not configured when this command is entered, the continue clause will go to the route-map entry with the next default sequence number.
If a route-map entry contains a continue clause and no match clause, the continue clause will be executed automatically.
Only inbound route-maps are supported.
Command Modes
Route-map configuration
Command History
12.0(22)S
This command was introduced.
12.3(2)T
This command was integrated into Cisco IOS Release 12.2(2)T.
Usage Guidelines
The continue command is used to configure continue clauses in inbound Border Gateway Protocol (BGP) route maps.
Route-map Operation Without Continue Clauses
A route-map evaluates match clauses until a successful match occurs. After the match occurs, the route-map stops evaluating match clauses and starts executing set clauses, in the order in which they were configured. If a successful match does not occur, the route-map "falls through" and evaluates the next sequence number of the route-map until all configured route-map entries have been evaluated or a successful match occurs. Each route map sequence is tagged with a sequence number to identify the entry. Route-map entries are evaluated in order starting with the lowest sequence number and ending with the highest sequence number. If the route-map contains only set clauses, the set clauses will be executed automatically, and the route-map will not evaluate any other route-map entries.
Route-map Operation With Continue Clauses
When a continue clause is configured, the route-map will continue to evaluate and execute match clauses in the specified route-map entry after a successful match occurs. The continue clause can be configured to go to (or jump to) a specific route-map entry by specifying the sequence number, or if a sequence number is not specified, the continue clause will go to the next sequence number. This behavior is called an "implied continue." If a match clause exists, the continue clause is executed only if a match occurs. If no successful matches occur, the continue clause is ignored.
Match Operations With Continue Clauses
If a match clause does not exist in the route-map entry but a continue clause does, the continue clause will be automatically executed and go to the specified route-map entry. If a match clause exists in a route-map entry, the continue clause is executed only when a successful match occurs. When a successful match occurs and a continue clause exists, the route-map executes the set clauses and then goes to the specified route-map entry. If the next route-map contains a continue clause, the route-map will execute the continue clause if a successful match occurs. If a continue clause does not exist in the next route-map, the route-map will be evaluated normally. If a continue clause exists in the next route-map but a match does not occur, the route-map will not continue and will "fall through" to the next sequence number if one exists.
Set Operations With Continue Clauses
Set clauses are saved during the match clause evaluation process and executed after the route-map evaluation is completed. The set clauses are evaluated and executed in the order in which they were configured. Set clauses are only executed after a successful match occurs, unless the route-map does not contain a match clause. The continue statement proceeds to the specified route-map entry only after configured set actions are performed. If a set action occurs in the first route-map and then the same set action occurs again, with a different value, in a subsequent route-map entry, the last set action will override any previous set actions that were configured with the same set command.
Note
Examples
In the following example, continue clause configuration is shown.
The first continue clause in route-map entry 10 indicates that the route-map will go to route map entry 30 if a successful matches occurs. If a match does not occur, the route-map will "fall through" to route-map entry 20. If a successful match occurs in route-map entry 20, the set action will be executed and the route map will not evaluate any additional route-map entries.
If a successful match does not occur in route-map entry 20, the route map will "fall through" to route-map entry 30. This sequence does not contain a match clause, so the set clause will be automatically executed and the continue clause will go to the next route-map entry because a sequence number is not specified.
If there are no successful matches, the route-map will "fall through" to route-map entry 30 and execute the set clause. Route-map entry 40 will not be evaluated.
Router(config)# route-map ROUTE-MAP-NAME permit 10Router(config-route-map)# match ip address 1Router(config-route-map)# match metric 10Router(config-route-map)# set as-path prepend 10Router(config-route-map)# continue 30Router(config-route-map)# exitRouter(config)# route-map ROUTE-MAP-NAME permit 20Router(config-route-map)# match ip address 2Router(config-route-map)# match metric 20Router(config-route-map)# set as-path prepend 10 10Router(config-route-map)# exitRouter(config)# route-map ROUTE-MAP-NAME permit 30Router(config-route-map)# set as-path prepend 10 10 10Router(config-route-map)# continueRouter(config-route-map)# exitRouter(config)# route-map ROUTE-MAP-NAME permit 40Router(config-route-map)# match community 10:1Router(config-route-map)# set local-preference 104Router(config-route-map)# exitRelated Commands
dampening
To configure a router to automatically dampen a flapping interface, use the dampening command in interface configuration mode. To disable automatic route dampening, use the no form of this command.
dampening [half-life-period reuse-threshold] [suppress-threshold max-suppress-time [restart-penalty]]
no dampening
Syntax Description
Defaults
This command is disabled by default. To manually configure the timer for the restart-penalty argument, the value for all arguments must be manually entered.
Command Modes
Interface configuration
Command History
12.0(22)S
This command was introduced.
12.2(13)T
This command was integrated into Cisco IOS Release 12.2(13)T.
Usage Guidelines
he IP Event Dampening feature will function on a subinterface but cannot be configured on only the subinterface. Only the primary interface can be configured with this feature, and all the subinterfaces are subject to the same dampening configuration.
When an interface is dampened, the interface is dampened to both IP and Connectionless Network Services (CLNS) routing equally. The interface is dampened to both IP and CLNS because integrated routing protocols like Intermediate System-to-Intermediate System (IS-IS), IP, and CLNS routing protocols are closely interconnected, so it is impossible to apply dampening separately.
This occurs because for integrated protocols like Intermediate System-to-Intermediate System (IS-IS), IP, and CLNS routing are closely interconnected, so it is impossible to apply dampening separately.
Copying a dampening configuration from virtual templates to virtual access interfaces is not supported because dampening has limited usefulness to existing applications using virtual templates. Virtual access interfaces are released when an interface flaps, and new connections and virtual access interfaces are acquired when the interface comes up and is made available to the network. Because dampening states are attached to the interface, the dampening states would not survive an interface flap.
If this command is applied to an interface that already has dampening configured, all dampening states are reset and the accumulated penalty will be set to 0. If the interface has been dampened, the accumulated penalty will fall into the reuse threshold range, and the dampened interface will be made available to the network. The flap counts, however, are retained.
Examples
The following example sets the half life to 30 seconds, the reuse threshold to 1500, the suppress threshold to 10000, and the maximum suppress time to 120 seconds:
interface Ethernet 0/0dampening 30 1500 10000 120The following example configures the router to apply a penalty of 500 on Ethernet interface 0/0 when the interface comes up for the first time after the router is reloaded:
interface Ethernet 0/0dampening 5 500 1000 20 500Related Commands
default-information
To control the candidate default routing information for Enhanced Interior Gateway Routing Protocol (EIGRP) processes, use the default-information command in router configuration mode. To suppress EIGRP candidate information in incoming or outbound updates, use the no default-information in command.
default-information {in | out} {access-list-number | access-list-name}
no default-information {in | out}
Syntax Description
Defaults
Normally, exterior routes are always accepted and default information is passed between EIGRP processes when redistribution occurs.
Command Modes
Router configuration
Command History
10.0
This command was introduced.
11.2
The access-list-number and access-list-name arguments were added.
Usage Guidelines
The default network of 0.0.0.0 used by Routing Information Protocol (RIP) cannot be redistributed by IGRP but can be redistributed by EIGRP.
Examples
The following example allows EIGRP exterior or default routes to be received by the EIGRP process in autonomous system 23:
router eigrp 23default-information indefault-information originate (BGP)
To configure a Border Gateway Protocol (BGP) routing process to distribute a default route (network 0.0.0.0), use the default-information originate command in address family or router configuration mode. To disable the advertisement of a default route, use the no form of this command.
default-information originate
no default-information originate
Syntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values
Command Modes
Address family configuration
Router configurationCommand History
10.0
This command was introduced.
12.0(7)T
Address family configuration mode support was added.
Usage Guidelines
The default-information originate command is used to configure a BGP routing process to advertise a default route (network 0.0.0.0). A redistribution statement must also be configured to complete this configuration or the default route will not be advertised.
The configuration of the default-information originate command in BGP is similar to the configuration of the network (BGP) command. The default-information originate command, however, requires explicit redistribution of the route 0.0.0.0. The network command requires only that the route 0.0.0.0 is present in the Interior Gateway Protocol (IGP) routing table. For this reason, the network command is preferred.
Note
Examples
In the following example, the router is configured to redistribute a default route from OSPF into the BGP routing process:
Router(config)# router bgp 50000Router(config-router)# address-family ipv4 unicastRouter(config-router-af)# default-information originateRouter(config-router-af)# redistribute ospf 100Router(config-router-af)# endRelated Commands
default-information originate (IS-IS)
To generate a default route into an IS-IS routing domain, use the default-information originate command in router configuration mode. 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.
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
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 link-state packets (LSPs).
Without a route map, the default is advertised only in Level 2 LSPs. For Level 1 routing, there is another mechanism to find the default route, which is to look for the closest Level 1 or Level 2 router. The closest Level 1 or Level 2 router can be found by looking at the attached-bit (ATT) in Level 1 LSPs.
A route map can be used for two purposes:
•
•
With a match ip address standard-access-list command, you can specify one or more IP routes that must exist before the router will advertise 0/0.
Examples
The following example forces the software 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 10.105.0.0access-list 2 permit 10.105.0.0 0.0.255.255Related Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
show isis database
Displays the IS-IS link-state database.
default-information originate (OSPF)
To generate a default external route into an OSPF routing domain, use the default-information originate command in router configuration mode. To disable this feature, use the no form of this command.
default-information originate [always] [metric metric-value] [metric-type type-value] [route-map map-name]
no default-information originate [always] [metric metric-value] [metric-type type-value] [route-map map-name]
Syntax Description
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
Usage Guidelines
Whenever you use the redistribute or the default-information router configuration command to redistribute routes into an OSPF routing domain, the Cisco IOS software automatically becomes an Autonomous System Boundary Router (ASBR). However, an ASBR does not, by default, generate a default route into the OSPF routing domain. The software still must 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 and argument. 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.
Examples
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 eigrp 108 metric 100 subnetsdefault-information originate metric 100 metric-type 1Related Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
default-information originate (RIP)
To generate a default route into Routing Information Protocol (RIP), use the default-information originate command in router configuration mode. To disable this feature, use the no form of this command.
default-information originate [route-map map-name]
no default-information originate
Syntax Description
route-map map-name
(Optional) Routing process will generate the default route if the route map is satisfied.
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
Usage Guidelines
The route map referenced in the default-information originate command cannot use an extended access list; it can use a standard access list.
Examples
The following example originates a default route (0.0.0.0/0) over a certain interface when 172.68.0.0/16 is present. Applying a condition (in this case a route map) to determine when the default route is originated is called "conditional default origination."
router ripversion 2network 172.68.16.0default-information originate route-map condition!route-map condition permit 10match ip address 10set interface s1/0!access-list 10 permit 172.68.16.0 0.0.0.255!default-metric (BGP)
To set a default metric for routes redistributed into Border Gateway Protocol (BGP), use the default-metric command in address family or router configuration mode. To remove the configured value and return BGP to default operation, use the no form of this command.
default-metric number
no default-metric number
Syntax Description
number
Default metric value applied to the redistributed route. The range of values for this argument is from 1 to 4294967295.
Defaults
The following is default behavior if this command is not configured or if the no form of this command is entered:
•
•
When this command is enabled, the metric for redistributed connected routes is set to 0.
Command Modes
Address family configuration
Router configurationCommand History
10.0
This command was introduced.
12.0(7)T
Address family configuration mode support was added.
Usage Guidelines
The default-metric command is used to set the metric value for routes redistributed into BGP with the redistribute command. A default metric can be configured to solve the problem of redistributing routes with incompatible metrics. Assigning the default metric will allow redistribution to occur.
This value is the Multi Exit Discriminator (MED) that is evaluated by BGP during the best path selection process. The MED is a non-transitive value that is processed only within the local autonomous system and adjacent autonomous systems. The default metric is not set if the received route has a MED value.
Note
Examples
In the following example, a metric of 1024 is set for routes redistributed into BGP from OSPF:
Router(config)# router bgp 50000Router(config-router)# address-family ipv4 unicastRouter(config-router-af)# default-metric 1024Router(config-router-af)# redistribute ospf 10Router(config-router-af)# endRelated Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
default-metric (EIGRP)
To set metrics for the Enhanced Interior Gateway Routing Protocol (EIGRP), use the default-metric command in router configuration mode. 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 mtu
Syntax Description
Defaults
Only connected routes can be redistributed without a default metric. The metric of redistributed connected routes is set to 0.
Command Modes
Address family configuration
Router configurationCommand History
Usage Guidelines
A default metric is required to redistribute a protocol into EIGRP. Automatic metric translations occur between IGRP and EIGRP. You do not need default metrics to redistributed IGRP or EIGRP into itself.
Note
Metric defaults have been carefully set to work for a wide variety of networks. Take great care when changing these values.
Keeping the same metrics is supported only when redistributing from IGRP, EIGRP, or static routes.
Examples
The following example takes redistributed Routing Information Protocol (RIP) metrics and translates them into EIGRP metrics with values as follows: bandwidth = 1000, delay = 100, reliability = 250, loading = 100, and MTU = 1500.
router eigrp 109network 172.16.0.0redistribute ripdefault-metric 1000 100 250 100 1500Related Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
default-metric (OSPF)
To set default metric values for the OSPF routing protocol, use the default-metric command in router configuration mode. To return to the default state, use the no form of this command.
default-metric metric-value
no default-metric metric-value
Syntax Description
Defaults
Built-in, automatic metric translations, as appropriate for each routing protocol. The metric of redistributed connected and static routes is set to 0.
Command Modes
Router configuration
Command History
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.
Note
Examples
The following example shows a router in autonomous system 109 using both the Routing Information Protocol (RIP) and the OSPF routing protocols. The example advertises OSPF-derived routes using RIP and assigns the Internal Gateway Protocol (IGP)-derived routes a RIP metric of 10.
router ripdefault-metric 10redistribute ospf 109Related Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
default-metric (RIP)
To set default metric values for Routing Information Protocol (RIP), use the default-metric command in router configuration mode. To return to the default state, use the no form of this command.
default-metric number-value
no default-metric [number-value]
Syntax Description
Defaults
Built-in, automatic metric translations, as appropriate for each routing protocol
Command Modes
Router configuration
Command History
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.
Examples
The following example shows a router in autonomous system 109 using both the RIP and the Open Shortest Path First (OSPF) routing protocols. The example advertises OSPF-derived routes using RIP and assigns the OSPF-derived routes a RIP metric of 10.
router ripdefault-metric 10redistribute ospf 109Related Commands
redistribute (IP)
Redistributes routes from one routing domain into another routing domain.
discard-route
To reinstall either an external or internal discard route that was previously removed, use the discard-route command in router configuration mode. To remove either an external or internal discard route, use the no form of this command.
discard-route [external | internal]
no discard-route [external | internal]
Syntax Description
Defaults
External and internal discard route entries are installed.
Command Modes
Router configuration
Command History
Usage Guidelines
External and internal discard route entries are installed in routing tables by default. During route summarization, routing loops may occur when data is sent to a nonexisting network that appears to be a part of the summary, and the router performing the summarization has a less specific route (pointing back to the sending router) for this network in its routing table. To prevent the routing loop, a discard route entry is installed in the routing table of the ABR or ASBR.
If for any reason you do not want to use the external or internal discard route, remove the discard route by entering the no discard-route command with either the external or internal keyword.
Examples
The following display shows the discard route functionality installed by default. When external or internal routes are summarized, a summary route to Null0 will appear in the router output from the show ip route command. See the router output lines that appear in bold font:
Router# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2ia - IS-IS inter area, * - candidate default, U - per-user static routeo - ODR, P - periodic downloaded static routeGateway of last resort is not set172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksC 172.16.0.128/25 is directly connected, Loopback1O 172.16.0.0/24 is a summary, 00:00:14, Null0C 172.16.0.0/25 is directly connected, Loopback0172.31.0.0/24 is variably subnetted, 3 subnets, 2 masksC 172.31.0.128/25 is directly connected, Loopback3O 172.31.0.0/24 is a summary, 00:00:02, Null0C 172.31.0.0/25 is directly connected, Loopback2C 192.168.0.0/24 is directly connected, Ethernet0/0RouterB# show ip route ospf172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksO 172.16.0.0/24 is a summary, 00:00:29, Null0172.16.0.0/24 is variably subnetted, 3 subnets, 2 masksO 201.0.0.0/24 is a summary, 00:00:17, Null0When the no discard-route command with the internal keyword is entered, notice the following route change, indicated by the router output lines that appear in bold font:
RouterB# configure terminalEnter configuration commands, one per line. End with CNTL/Z.RouterB(config)# router ospf 1RouterB(config-router)# no discard-route internalRouterB(config-router)#endRouterB# show ip route ospf172.31.0.0/24 is variably subnetted, 3 subnets, 2 masksO 172.16.0.0/24 is a summary, 00:04:14, Null0Next, the no discard-route command with the external keyword is entered to remove the external discard route entry:
RouterB# configure terminalEnter configuration commands, one per line. End with CNTL/Z.RouterB(config)# router ospf 1RouterB(config-router)# no discard-route externalRouterB(config-router)# endThe following router output from the show running-config command confirms that both the external and internal discard routes have been removed from the routing table of RouterB. See the router output lines that appear in bold font:
RouterB# show running-configBuilding configuration...Current configuration : 1114 bytes!version 12.2service timestamps debug uptimeservice timestamps log uptimeno service password-encryption!hostname RouterB...router ospf 1log-adjacency-changesno discard-route externalno discard-route internalarea 1 range 172.16.0.0 255.255.255.0summary-address 172.31.0.0 255.255.255.0redistribute rip subnetsnetwork 192.168.0.0 0.0.0.255 area 0network 172.16.0.0 0.0.0.255 area 1!Related Commands
distance (IP)
To define an administrative distance, use the distance command in router configuration mode. To remove a distance definition, use the no form of this command.
distance {ip-address {wildcard-mask}} [ip-standard-list] [ip-extended-list]
no distance {ip-address {wildcard-mask}} [ip-standard-list] [ip-extended-list]
Syntax Description
Defaults
For more information on default administrative distance, see "Usage Guidelines."
Command Modes
Router configuration
Command History
Usage Guidelines
Table 2 lists default administrative distances.
Numerically, an administrative distance is an integer from 0 to 255. In general, the higher the value, the lower the trust rating. An administrative distance of 255 means that 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 option 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 the "Examples" section for further clarification).
For BGP, the distance command sets the administrative distance of the External BGP (EBGP) route.
For OSPF, the IP address and address mask entered for the distance command should match the source address and address mask of the OSPF router that sent the link-state advertisement (LSA).
The show ip protocols EXEC command displays the default administrative distance for a specified routing process.
Always set the administrative distance from the least to the most specific network.
Note
Examples
In the following example, the router eigrp global configuration command sets up EIGRP routing in autonomous system number 109. The network router configuration commands specify EIGRP routing on networks 192.168.7.0 and 172.16.0.0. The first distance router configuration command sets the default administrative distance to 255, which instructs the Cisco IOS software 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 192.168.7.0 to 90. The third distance command sets the administrative distance for the router with the address 172.16.1.3 to 120.
router eigrp 109network 192.168.7.0network 172.16.0.0distance 255distance 90 192.168.7.0 0.0.0.255distance 120 172.16.1.3 0.0.0.0In the following example, the set distance is from the least to the most specific network:
router eigrp 100network 10.0.0.0distance 22 10.0.0.0distance 33 10.11.0.0 0.0.255.255distance 44 10.11.12.0 0.0.0.255
Note
Related Commands
distance bgp
Allows the use of external, internal, and local administrative distances that could be a better route to a node.
distance bgp
To configure the administrative distance for BGP routes, use the distance bgp command in address family or router configuration mode. To return to the administrative distance to the default value, use the no form of this command.
distance bgp external-distance internal-distance local-distance
no distance bgp
Syntax Description
Defaults
The following values are used if this command is not configured or if the no form is entered:
external-distance: 20
internal-distance: 200
local-distance: 200Routes with a distance of 255 are not installed in the routing table.
Command Modes
Address family configuration
Router configurationCommand History
10.0
This command was introduced.
12.0(7)T
Address family configuration mode support was added.
Usage Guidelines
The distance bgp command is used to configure 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 a positive integer from 1 to 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 (eBGP), or if some internal routes should be preferred by BGP.
Caution
The distance bgp command replaces the distance mbgp command.
Examples
In the following example, the external distance is set to 10, the internal distance is set to 50, and the local distance is set to 100:
Router(config)# router bgp 50000Router(config-router)# address family ipv4 multicastRouter(config-router-af)# network 10.108.0.0Router(config-router-af)# neighbor 192.168.6.6 remote-as 123Router(config-router-af)# neighbor 172.16.1.1 remote-as 47Router(config-router-af)# distance bgp 10 50 100Router(config-router-af)# endRelated Commands
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 command in router configuration mode. To reset these values to their defaults, use the no form of this command.
distance eigrp internal-distance external-distance
no distance eigrp
Syntax Description
Defaults
internal-distance: 90
external-distance: 170
Command Modes
Router configuration
Command History
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 from 0 to 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 EIGRP, or if some internal routes should really be preferred by EIGRP.
Table 3 lists the default administrative distances.
To display the default administrative distance for a specified routing process, use the show ip protocols EXEC command.
Examples
In the following example, the router eigrp global configuration command sets up EIGRP routing in autonomous system number 109. The network router configuration commands specify EIGRP routing on networks 192.168.7.0 and 172.16.0.0. The distance eigrp command sets the administrative distance of all EIGRP internal routes to 80 and all EIGRP external routes to 130.
Router(config)# router eigrp 109Router(router-config)# network 192.168.7.0Router(router-config)# network 172.16.0.0Router(router-config)# distance eigrp 80 130Related Commands
show ip protocols
Displays the parameters and current state of the active routing protocol process.
distance ospf
To define OSPF route administrative distances based on route type, use the distance ospf command in router configuration mode. To restore the default value, use the no form of this command.
distance ospf {[intra-area dist1] [inter-area dist2] [external dist3]}
no distance ospf
Syntax Description
Defaults
dist1: 110
dist2: 110
dist3: 110
Command Modes
Router configuration
Command History
Usage Guidelines
You must specify at least one of the keyword-argument pairs.
This command performs the same function as the distance command used with an access list. However, the distance ospf command allows you to set a distance for an entire group of routes, rather than a specific route that passes an access list.
If you already have configured the distance (IP) command with a source IP address and address mask, it will take precendence over the distance ospf command.
A common reason to use the distance ospf command is when you have multiple OSPF processes with mutual redistribution, and you want to prefer internal routes from one over external routes from the other.
Examples
The following example changes the external distance to 200, making the route less reliable:
Router A Configuration
router ospf 1redistribute ospf 2 subnetdistance ospf external 200!router ospf 2redistribute ospf 1 subnetdistance ospf external 200Router B Configuration
router ospf 1 redistribute ospf 2 subnetdistance ospf external 200 ! router ospf 2redistribute ospf 1 subnetdistance ospf external 200Related Commands
distribute-list in (BGP)
To filter routes or networks received in incoming Border Gateway Protocol (BGP) updates, use the distribute-list in command in router configuration mode. To delete the distribute list and remove from the running configuration file, use the no form of this command.
distribute-list acl-number | prefix list-name in
no distribute-list acl-number | prefix list-name in
Syntax Description
Note
Defaults
If this command is configured without a predefined access list or prefix list, the distribute list will default to permitting all traffic.
Command Modes
Router configuration
Note
Command History
10.0
This command was introduced.
11.2
The acl-number arguments was added.
12.0
The prefix list-name argument was added.
Usage Guidelines
The distribute-list in command is used to filter incoming BGP updates. An access list or prefix list must be defined prior to configuration of this command. Standard and expanded access lists are supported. IP prefix lists are used to filter based on the bit length of the prefix. An entire network, subnet, supernet, or single host route can be specified. Prefix list and access list configuration is mutually exclusive when configuring a distribute list. The session must be reset with the clear ip bgp command before the distribute list will take effect.
Note
To suppress networks from being advertised in updates, use the distribute-list out command.
Examples
In the following example, a prefix list and distribute list are defined to configure the BGP routing process to accept traffic from only network 192.168.1.0 and network 10.108.0.0. An inbound route refresh is initiated to activate the distribute-list.
Router(config)# ip prefix-list RED deny 0.0.0.0/0 le 32Router(config)# ip prefix-1ist RED permit 10.108.0.0/16Router(config)# ip prefix-list RED permit 192.168.1.0/24Router(config)# !Router(config)# router bgp 50000Router(config-router)# network 10.108.0.0Router(config-router)# distribute-list prefix RED inRouter(config-router)# endRouter# clear ip bgp inIn the following example, an access list and distribute list are defined to configure the BGP routing process to accept traffic from only network 192.168.1.0 and network 10.108.0.0. An inbound route refresh is initiated to activate the distribute-list.
Router(config)# access-list 1 deny 0.0.0.0 255.255.255.255Router(config)# access-list 1 permit 192.168.1.0Router(config)# access-list 1 permit 10.108.0.0Router(config)# !Router(config)# router bgp 50000Router(config-router)# network 10.108.0.0Router(config-router)# distribute-list 1 inRouter(config-router)# endRouter# clear ip bgp inRelated Commands
distribute-list in (IP)
To filter networks received in updates, use the distribute-list in command in address family or router configuration mode. To change or cancel the filter, use the no form of this command.
distribute-list [access-list-number | name] | [route-map map-tag] in [interface-type | interface-number]
no distribute-list [access-list-number | name] | [route-map map-tag] in [interface-type | interface-number]
Syntax Description
Defaults
This command is disabled by default.
Command Modes
Address family configuration
Router configurationCommand History
Usage Guidelines
This command must specify either an access list or a map-tag name of a route map. The route map is supported for OSPF filtering only.
The interface-type and interface-type arguments cannot be used in address family configuration mode.
OSPF routes cannot be filtered from entering the OSPF database. If you use this command for OSPF, it only filters routes from the routing table; it does not prevent link-state packets from being propagated.
If a route map is specified, the route map can be based on the following match options:
•
•
•
•
•
•
•
Configure the route map before specifying it in the distribute-list in command.
Examples
In the following example, the EIGRP routing process accepts only two networks—network 0.0.0.0 and network 10.108.0.0:
access-list 1 permit 0.0.0.0access-list 1 permit 10.108.0.0access-list 1 deny 0.0.0.0 255.255.255.255router eigrpnetwork 10.108.0.0distribute-list 1 inIn the following example, OSPF external LSAs have a tag. The value of the tag is examined before the prefix is installed in the routing table. All OSPF external prefixes that have the tag value of 777 are filtered (prevented from being installed in the routing table). The permit statement with sequence number 20 has no match conditions, and there are no other route-map statements after sequence number 20, so all other conditions are permitted.
route-map tag-filter deny 10match tag 777route-map tag-filter permit 20!router ospf 1router-id 10.0.0.2log-adjacency-changesnetwork 172.16.2.1 0.0.0.255 area 0distribute-list route-map tag-filter inRelated Commands
distribute-list out (BGP)
To suppress networks from being advertised in outbound Border Gateway Protocol (BGP) updates, use the distribute-list out command in router configuration mode. To delete the distribute list and remove from the running configuration file, use the no form of this command.
distribute-list acl-number | prefix list-name out [protocol process-number | connected | static]
no distribute-list acl-number | prefix list-name out [protocol process-number | connected | static]
Syntax Description
Note
Defaults
If this command is configured without a predefined access list or prefix list, the distribute list will default to permitting all traffic.
Command Modes
Router configuration
Command History
10.0
This command was introduced.
11.2
The acl-number argument was added.
12.0
The prefix list-name argument was added.
Usage Guidelines
The distribute-list out command is used to filter outbound BGP updates. An access list or prefix list must be defined prior to configuration of this command. Standard and expanded access lists are supported. IP prefix lists are used to filter based on the bit length of the prefix. An entire network, subnet, supernet, or single host route can be specified. Prefix list and access list configuration is mutually exclusive when configuring a distribute list. The session must be reset with the clear ip bgp command before the distribute list will take effect.
Note
Entering a protocol and/or process-number arguments causes the distribute list to be applied to only routes derived from the specified routing process. Addresses not specified in the distribute-list command will not be advertised in outgoing routing updates after a distribute list is configured.
To suppress networks or routes from being received in inbound updates, use the distribute-list in command.
Examples
In the following example, a prefix list and distribute list are defined to configure the BGP routing process to advertise only network 192.168.0.0. An outbound route refresh is initiated to activate the distribute-list.
Router(config)# ip prefix-list BLUE deny 0.0.0.0/0 le 32Router(config)# ip prefix-list BLUE permit 192.168.0.0/16Router(config)# !Router(config)# router bgp 50000Router(config-router)# distribute-list prefix BLUE outRouter(config-router)# endRouter# clear ip bgp outIn the following example, an access list and a distribute list are defined to configure the BGP routing process to advertise only network 192.168.0.0. An outbound route refresh is initiated to activate the distribute-list.
Router(config)# access-list 1 permit 192.168.0.0 0.0.255.255Router(config)# access-list 1 deny 0.0.0.0 255.255.255.255Router(config)# !Router(config)# router bgp 50000Router(config-router)# distribute-list 1 outRouter(config-router)# endRouter# clear ip bgp outRelated Commands
distribute-list out (IP)
To suppress networks from being advertised in updates, use the distribute-list out command in address family or router configuration mode. To cancel this function, use the no form of this command.
distribute-list {access-list-number | access-list-name} out [interface-name | routing-process | as-number]
no distribute-list {access-list-number | access-list-name} out [interface-name | routing-process | as-number]
Syntax Description
Defaults
This command is disabled by default.
Command Modes
Address family configuration
Router configurationCommand History
10.0
This command was introduced.
11.2
The access-list-name argument was added.
12.0(7)T
Address family configuration mode was added.
Usage Guidelines
When networks are redistributed, a routing process name can be specified as an optional trailing argument to the distribute-list command. Specifying this option causes the access list to be applied to only those routes derived from the specified routing process. After the process-specific access list is applied, any access list specified by a distribute-list command without a process name argument will be applied. Addresses not specified in the distribute-list command will not be advertised in outgoing routing updates.
The interface-name argument cannot be used in address family configuration mode.
Note
Examples
The following example would cause only one network to be advertised by a RIP routing process, network 10.108.0.0:
access-list 1 permit 10.108.0.0access-list 1 deny 0.0.0.0 255.255.255.255router ripnetwork 10.108.0.0distribute-list 1 outThe following example applies access list 1 to outgoing routing updates and enables Intermediate System-to-Intermediate System (IS-IS) on Ethernet interface 0. Only network 10.10.101.0 will be advertised in outgoing IS-IS routing updates.
router isisredistribute ospf 109distribute-list 1 outinterface Ethernet 0ip router isisaccess-list 1 permit 10.10.101.0 0.0.0.255Related Commands
domain-password
To configure the IS-IS routing domain authentication password, use the domain-password command in router configuration mode. To disable a password, use the no form of this command.
domain-password password [authenticate snp {validate | send-only}]
no domain-password [password]
Syntax Description
Defaults
No domain password is specified and no authentication is enabled for exchange of Level 2 routing information.
Command Modes
Router configuration
Command History
10.0
This command was introduced.
12.0(21)ST
The authenticate snp, validate, and send-only keywords were added.
Usage Guidelines
This password is exchanged as plain text and thus this feature provides only limited security.
This password is inserted in Level 2 (area router level) PDU link-state packets (LSPs), complete sequence number PDUs (CSNPs), and partial sequence number PDUs (PSNPs).
If you do not specify the authenticate snp keyword along with either the validate or send-only keyword, then the IS-IS routing protocol does not insert the password into SNPs.
Examples
The following example assigns an authentication password to the routing domain and specifies that the password be inserted in SNPs and checked in SNPs that the system receives:
router isisdomain-password users2j45 authenticate snp validateRelated Commands
area-password
Configures the IS-IS area authentication password.
isis password
Configures the authentication password for an interface.
eigrp log-neighbor-changes
To enable the logging of changes in Enhanced Interior Gateway Routing Protocol (EIGRP) neighbor adjacencies, use the eigrp log-neighbor-changes command in router configuration mode. To disable the logging of changes in EIGRP neighbor adjacencies, use the no form of this command.
eigrp log-neighbor-changes
no eigrp log-neighbor-changes
Syntax Description
This command has no arguments or keywords.
Defaults
Adjacency changes are logged.
Command Modes
Router configuration
Command History
Usage Guidelines
This command enables the logging of neighbor adjacency changes to monitor the stability of the routing system and to help detect problems. Logging is enabled by default. To disable the logging of neighbor adjacency changes, use the no form of this command.
Examples
The following configuration disables logging of neighbor changes for EIGRP process 209:
router eigrp 209no eigrp log-neighbor-changesThe following configuration enables logging of neighbor changes for EIGRP process 209:
router eigrp 209eigrp log-neighbor-changeseigrp log-neighbor-warnings
To enable the logging of Enhanced Interior Gateway Routing Protocol (EIGRP) neighbor warning messages, use the eigrp log-neighbor-warnings command in router configuration mode. To disable the logging of EIGRP neighbor warning messages, use the no form of this command.
eigrp log-neighbor-warnings [seconds]
no eigrp log-neighbor-warnings
Syntax Description
seconds
(Optional) The time interval (in seconds) between repeated neighbor warning messages. The range of seconds is from 1 to 65535.
Defaults
Neighbor warning messages are logged.
Command Modes
Router configuration
Command History
Usage Guidelines
When neighbor warning messages occur, they are logged by default. With this command, you can disable and enable neighbor warning messages, and configure the interval between repeated neighbor warning messages.
Examples
The following command will log neighbor warning messages for EIGRP process 209 and repeat the warning messages in 5-minute (300 seconds) intervals:
router eigrp 209eigrp log-neighbor-warnings 300eigrp router-id
To set the router ID used by Enhanced Interior Gateway Routing Protocol (EIGRP) when communicating with its neighbors, use the eigrp router-id command in router configuration mode. To remove the configured router ID, use the no form of this command.
eigrp router-id ip-address
no eigrp router-id ip-address
Syntax Description
Defaults
EIGRP automatically selects an IP address to use as the router ID when an EIGRP process is started. The highest local IP address is selected and loopback interfaces are preferred. The router ID is not changed unless the EIGRP process is removed with the no router eigrp command or if the router ID is manually configured with the eigrp router-id command.
Command Modes
Address family configuration
Router configurationCommand History
Usage Guidelines
The router ID is used to identify the originating router for external routes. If an external route is received with the local router ID, the route is discarded. The router ID can be configured with any IP address with two exceptions; 0.0.0.0 and 255.255.255.255 are not legal values and cannot be entered. A unique value should be configured for each router.
Examples
The following example configures 172.16.1.3 as a fixed router ID:
router eigrp 209eigrp router-id 172.16.1.3eigrp stub
To configure a router as a stub using Enhanced Interior Gateway Routing Protocol (EIGRP), use the eigrp stub command in router configuration mode. To disable the EIGRP stub routing feature, use the no form of this command.
eigrp stub [receive-only | connected | static | summary]
no eigrp stub [receive-only | connected | static | summary]
Syntax Description
Defaults
Stub routing is not enabled by default.
Command Modes
Router configuration
Command History
12.0(7)T
This command was introduced.
12.0(15)S
This command was integrated into Cisco IOS Release 12.0(15)S.
Usage Guidelines
Use the eigrp stub command to configure a router as a stub where the router directs all IP traffic to a distribution router.
The eigrp stub command can be modified with several options, and these options can be used in any combination except for the receive-only keyword. The receive-only keyword will restrict the router from sharing any of its routes with any other router in that EIGRP autonomous system, and the receive-only keyword will not permit any other option to be specified because it prevents any type of route from being sent. The three other optional keywords (connected, static, and summary) can be used in any combination but cannot be used with the receive-only keyword. If any of these three keywords is used individually with the eigrp stub command, connected and summary routes will not be sent automatically.
The connected keyword will permit the EIGRP Stub Routing feature to send connected routes. If the connected routes are not covered by a network statement, it may be necessary to redistribute connected routes with the redistribute connected command under the EIGRP process. This option is enabled by default.
The static keyword will permit the EIGRP Stub Routing feature to send static routes. Without the configuration of this option, EIGRP will not send any static routes, including internal static routes that normally would be automatically redistributed. It will still be necessary to redistribute static routes with the redistribute static command.
The summary keyword will permit the EIGRP Stub Routing feature to send summary routes. Summary routes can be created manually with the summary address command or automatically at a major network border router with the auto-summary command enabled. This option is enabled by default.
Note
Examples
In the following example, the eigrp stub command is used to configure the router as a stub that advertises connected and summary routes:
router eigrp 1network 10.0.0.0eigrp stubIn the following example, the eigrp stub command is issued with the connected and static keywords to configure the router as a stub that advertises connected and static routes (sending summary routes will not be permitted):
router eigrp 1network 10.0.0.0eigrp stub connected staticIn the following example, the eigrp stub command is issued with the receive-only keyword to configure the router as a receive-only neighbor (connected, summary, and static routes will not be sent):
router eigrp 1network 10.0.0.0 eigrpeigrp stub receive-onlyexit peer-policy
To exit policy-template configuration mode and enter router configuration mode, use the exit peer-policy command in policy-template configuration mode.
exit peer-policy
Syntax Description
This command has no keywords or arguments.
Defaults
No default behavior or values
Command Modes
Policy-template configuration
Command History
Usage Guidelines
This command is used to exit policy-template configuration mode.
Examples
In the following example, the router is configured to exit policy-template configuration mode and enter router configuration mode:
Router(config-router-ptmp)# exit-peer-policyRouter(config-router)#Related Commands
template peer-policy
Creates a peer policy template and enters policy-template configuration mode.
exit peer-session
To exit session-template configuration mode and enter router configuration mode, use the exit peer-session command in session-template configuration mode.
exit peer-session
Syntax Description
This command has no keywords or arguments.
Defaults
No default behavior or values
Command Modes
Session-template configuration
Command History
Usage Guidelines
This command is used to exit session-template configuration mode.
Examples
In the following example, the router is configured to exit session-template configuration mode and enter router configuration mode:
Router(config-router-stmp)# exit-peer-sessionRouter(config-router)#Related Commands
template peer-session
Creates a peer session template and enters session-template configuration mode.
exit-address-family
To exit from address family configuration mode, use the exit-address-family command in address family configuration mode.
exit-address-family
Syntax Description
This command has no arguments or keywords.
Defaults
No default behavior or values
Command Modes
Address family configuration
Command History
12.0(5)T
This command was introduced.
12.0(22)S
EIGRP support was added.
12.2(15)T
EIGRP support was added.
Usage Guidelines
This command is used to exit address family configuration mode.
Examples
In the following example, the router is configured exit address family configuration mode:
Router(config-router-af)# exit-address-familyRouter(config-router-af)#Related Commands
export map
To associate an export map with a VPN Routing and Forwarding (VRF) instance, use the export map command in VRF configuration mode.
export map route-map
Syntax Description
Defaults
No default behavior or values
Command Modes
IP VPN Routing/Forwarding configuration mode
Command History
Usage Guidelines
The export map command is used to associate a route map with the specified VRF. The export map is used to filter routes that are eligible for export out of a VRF, based on the route target extended community attributes of the route. Only one export route map can be configured for a VRF.
An export route map can be used when an application requires finer control over the routes that are exported out of a VRF than the control that is provided by import and export extended communities configured for the importing and exporting VRFs.
Examples
In the following example, an export is configured under the VRF and an access list and route map are configured to specify which prefixes are exported:
Router(config)# ip vrf REDRouter(config-vrf)# rd 1:1Router(config-vrf)# export map BLUERouter(config-vrf)# route-target import 2:1Router(config-vrf)# exitRouter(config)# access-list 1 permit 192.168.0.0 0.0.255.255Router(config)# route-map BLUE permit 10Router(config-route-map)# match ip address 1Router(config-route-map)# set extcommunity rt 2:1Router(config-route-map)# endRelated Commands
fast-flood
To fast-flood Intermediate System-to-Intermediate System (IS-IS) link-state packets (LSPs), use the fast-flood command in router configuration mode. To disable the fast-flooding, use the no version of this command.
fast-flood lsp-number
no fast-flood lsp-number
Syntax Description
lsp-number
(Optional) The number of LSPs from 1 to 15 to be flooded before shortest path first (SPF) is started. The default is 5 LSPs.
Command Modes
Router configuration
Defaults
Fast-flooding is disabled. Five LSPs are flooded before SPF is started.
Command History
12.0(27)S
This command was introduced.
12.3(7)T
This command was integrated into Cisco IOS Release 12.3(7)T. This command replaces the ip fast-convergence command.
Usage Guidelines
The fast-flood command tells the router to flood a certain number of LSPs, as configured by the lsp-number argument (if no lsp-number value has been specified, the default value of 5 is used), that invoke SPF before running SPF. When you speed up the LSP flooding process, you improve overall network convergence time.
If you are running SPF and if you have configured very short values (less than 40 milliseconds) for the initial delay that is set by the seconds argument of the incremental-spf command, the SPF computation might start before the LSP that triggered SPF is flooded to neighbors. The router should always flood (at least) the LSP that triggered SPF before the router runs the SPF computation.
We recommend that you enable the fast-flooding of LSPs before the router runs the SPF computation, in order to achieve a faster convergence time.
Note
Examples
In the following example, the fast-flood command is entered to configure the router to flood the first seven LSPs that invoke SPF, before the SPF computation is started. When the show running-configuration command is entered, the output confirms that fast-flooding has been enabled on the router.
Router# clear isis rib redistribution 10.1.0.0 255.255.0.0Router> enableRouter# configure terminalRouter(config)# router isis firstRouter(config-router)# fast-flood 7Router(config-router)# endRouter# show running-configurationfast-flood 7Related Commands
flash-update-threshold
To suppress regularly scheduled flash updates, use the flash-update-threshold command in router configuration mode. To return to the default state, use the no form of this command.
flash-update-threshold seconds
no flash-update-threshold
Syntax Description
seconds
The time interval in seconds for which the suppression of flash updates can be configured. The range is from 1 to 30 seconds.
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
Usage Guidelines
This command suppresses flash updates when the arrival of a regularly scheduled update matches the number of seconds that is configured with the seconds argument. The range of seconds that can be configure is from 0 to 30 seconds. If the number of seconds matches the number of seconds or is less than the number seconds that is configured with the seconds argument, the flash update is suppressed. If the numbers seconds until the flash update arrives exceeds the number of seconds that is configured with the seconds argument, the flash update is not suppressed. The regular scheduled interval for flash updates and the configuration of the suppression of flash updates can be verified with the show ip protocol command.
Examples
The following example configures a router to suppress a regularly scheduled flash update if the update is due in 10 seconds or less:
router ripflash-update-threshold 10Related Commands
show ip protocols
Displays the parameters and current state of the active routing protocol process.
hello padding
To reenable IS-IS hello padding at the router level, enter the hello padding command in router configuration mode. To disable IS-IS hello padding, use the no form of this command.
hello padding
no hello padding
Syntax Description
This command has no arguments or keywords.
Defaults
IS-IS hello padding is enabled.
Command Modes
Router configuration
Command History
12.0(5)T
This command was introduced.
12.0(5)S
This command was integrated into Cisco IOS Release 12.0(5)S.
Usage Guidelines
Intermediate System-to-Intermediate System (IS-IS) hellos are padded to the full maximum transmission unit (MTU) size. The benefit of padding IS-IS hellos to the full MTU is that it allows for early detection of errors that result from transmission problems with large frames or errors that result from mismatched MTUs on adjacent interfaces.
You can disable hello padding in order to avoid wasting network bandwidth in case the MTU of both interfaces is the same or, in case of translational bridging. While hello padding is disabled, Cisco routers still send the first five IS-IS hellos padded to the full MTU size, in order to maintain the benefits of discovering MTU mismatches.
To disable hello padding for all interfaces on a router for the IS-IS routing process, enter the no hello padding command in router configuration mode. To selectively disable hello padding for a specific interface, enter the no isis hello padding command in interface configuration mode.
Examples
In the following example the no hello padding command is used to turn off hello padding at the router level:
Router(config)# router isisRouter(config-router)# no hello paddingRouter(config-router)# endThe show clns interfaces command is entered to show that hello padding has been turned off at router level:
Router# show clns interface e0/0Ethernet0/0 is up, line protocol is upChecksums enabled, MTU 1497, Encapsulation SAPERPDUs enabled, min. interval 10 msec.CLNS fast switching enabledCLNS SSE switching disabledDEC compatibility mode OFF for this interfaceNext ESH/ISH in 4 secondsRouting Protocol: IS-ISCircuit Type: level-1-2Interface number 0x0, local circuit ID 0x1Level-1 Metric: 10, Priority: 64, Circuit ID: Router_B.01Level-1 IPv6 Metric: 10Number of active level-1 adjacencies: 1Level-2 Metric: 10, Priority: 64, Circuit ID: Router_B.01Level-2 IPv6 Metric: 10Number of active level-2 adjacencies: 1Next IS-IS LAN Level-1 Hello in 6 seconds! No hello paddingNext IS-IS LAN Level-2 Hello in 2 seconds! No hello paddingWhen the debug isis adj packets command is entered, the output will show the IS-IS hello protocol data unit (PDU) length when a hello packet has been sent to or received from an IS-IS adjacency. In the following example the IS-IS hello PDU length is 1497:
Router# debug isis adj packets e0/0IS-IS Adjacency related packets debugging is onRouter_A#*Oct 11 18:04:17.455: ISIS-Adj: Sending L1 LAN IIH on Ethernet0/0, length 55*Oct 11 18:04:19.075: ISIS-Adj: Rec L2 IIH from aabb.cc00.6600 (Ethernet0/0), cir type L1L2, cir id 0000.0000.000B.01, length 1497Related Commands
hostname dynamic
To enable IS-IS dynamic hostname capability on the router, use the hostname dynamic command in router configuration mode. To disable the dynamic hostname feature, use the no form of this command.
hostname dynamic
no hostname dynamic
Syntax Description
This command has no arguments or keywords.
Command Default
The dynamic hostname feature is enabled by default.
Command Modes
Router configuration
Command History
12.0
This command was introduced.
12.0S
This command was integrated into Cisco IOS Release 12.0(S).
Usage Guidelines
In the IS-IS routing domain, the system ID is used to represent each router. The system ID is part of the network entity title (NET) that is configured for each IS-IS router. For example, a router with a configured NET of 49.0001.0023.0003.000a.00 has a system ID of 0023.0003.000a. Router-name-to-system-ID mapping is difficult for network administrators to remember during maintenance and troubleshooting on the routers. Entering the show isis hostname command displays the entries in the system-ID-to-router-name mapping table.
The dynamic hostname mechanism uses link-state protocol (LSP) flooding to distribute the router-name-to-system-ID mapping information across the entire network. Every router on the network will try to install the system ID-to-router name mapping information in its routing table.
If a router that has been advertising the dynamic name type, length, value (TLV) on the network suddenly stops the advertisement, the mapping information last received will remain in the dynamic host mapping table for up to one hour, allowing the network administrator to display the entries in the mapping entry during a time when the network experiences problems. Entering the show isis hostname command displays the entries in the mapping table.
Note
Examples
The following example changes the hostname from Router to RouterA and assigns the NET 49.0001.0000.0000.000b.00 to RouterA. The dynamic hostname feature is disabled by entering the no dynamic hostname command. The dynamic hostname feature is then reeanabled by entering the dynamic hostname command.
Router> enableRouter# configure terminalRouter(config)# hostname RouterARouterA(config)# router isis CompanyARouterA(config-router)# net 49.0001.0000.0000.000b.00RouterA(config-router)# hostname dynamicRouterA(config-router)# endEntering the show isis hostname command displays the dynamic host mapping table. The * symbol signifies that this is the hostname for the local router. The dynamic host mapping table confirms that system ID 0000.0000.000B belongs to a router with the dynamic hostname RouterA. This router is running the IS-IS process named CompanyA.
Router# show isis hostnameLevel System ID Dynamic Hostname (CompanyA)* 0000.0000.000B RouterARelated Commands
