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Cisco IOS IP Command Reference, Volume 2 of 4: Routing Protocols, Release 12.3
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Introduction
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IP Routing Protocol Commands: A through B
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IP Routing Protocols Commands: C through H
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IP Routing Protocols Commands: I
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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 local policy
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IP Routing Protocols Commands: show ip ospf through version
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Table Of Contents
redistribute (BGP to ISO IS-IS)
redistribute (ISO ISIS to BGP)
offset-list (RIP)
To add an offset to incoming and outgoing metrics to routes learned via Routing Information Protocol (RIP), use the offset-list command in router configuration mode. To remove an offset list, use the no form of this command.
offset-list {access-list-number | access-list-name} {in | out} offset [interface-type interface-number]
no offset-list {access-list-number | access-list-name} {in | out} offset [interface-type interface-number]
Syntax Description
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
10.0
This command was introduced.
10.3
The interface-type and interface-number arguments were added.
11.2
The access-list-name argument was added.
Usage Guidelines
The offset value is added to the routing metric. An offset list with an interface type and interface number is considered extended and takes precedence over an offset list that is not extended. Therefore, if an entry passes the extended offset list and the normal offset list, the offset of the extended offset list is added to the metric.
Examples
In the following example, the router applies an offset of 10 to the delay component of a router only to access list 21:
offset-list 21 out 10In the following example, the router applies an offset of 10 to routes learned from Ethernet interface 0:
offset-list 21 in 10 ethernet 0offset-list (EIGRP)
To add an offset to incoming and outgoing metrics to routes learned via Enhanced Interior Gateway Routing Protocol (EIGRP), use the offset-list command in router configuration mode. To remove an offset list, use the no form of this command.
offset-list {access-list-number | access-list-name} {in | out} offset [interface-type interface-number]
no offset-list {access-list-number | access-list-name} {in | out} offset [interface-type interface-number]
Syntax Description
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
10.0
This command was introduced.
10.3
The interface-type and interface-number arguments were added.
11.2
The access-list-name argument was added.
Usage Guidelines
The offset value is added to the routing metric. An offset list with an interface type and interface number is considered extended and takes precedence over an offset list that is not extended. Therefore, if an entry passes the extended offset list and the normal offset list, the offset of the extended offset list is added to the metric.
Examples
In the following example, the router applies an offset of 10 to the delay component of the router only to access list 21:
offset-list 21 out 10In the following example, the router applies an offset of 10 to routes learned from Ethernet interface 0:
offset-list 21 in 10 ethernet 0output-delay
To change the interpacket delay for Routing Information Protocol (RIP) updates sent, use the output-delay command in router configuration mode. To remove the delay, use the no form of this command.
output-delay delay
no output-delay
Syntax Description
delay
Delay between packets in a multiple-packet RIP update (in milliseconds). The range is from 8 to 50. The default is 0.
Defaults
0 milliseconds
Command Modes
Router configuration
Command History
10.0
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
Consider using this command if you have a high-end router that is sending at high speed to a low-speed router that might not be able to receive at the high speed. Configuring this command will help prevent the routing table from losing information.
Examples
The following example sets the interpacket delay to 10 milliseconds:
router ripoutput-delay 10partition avoidance
To cause an IS-IS Level 1-2 border router to stop advertising the Level 1 area prefix into the Level 2 backbone when full connectivity is lost between the border router, all adjacent Level 1 routers, and end hosts, use the partition avoidance command in router configuration mode. To disable this output format, use the no form of the command.
partition avoidance area-tag
no partition avoidance area-tag
Syntax Description
Defaults
This command is disabled by default.
Command Modes
Router configuration
Command History
Usage Guidelines
When the partition avoidance command is enabled, a multiarea router withdraws a Level 1 area prefix from the Level 2 backbone when it no longer has any active adjacencies to that Level 1 area. This withdrawal prevents the Level 1 area from appearing to be partitioned within the Level 2 backbone.
In International Standards Organization (ISO) CLNS networks using a redundant topology, it is possible for an area to become "partitioned" when full connectivity is lost between a Level 1-2 border router, all adjacent Level 1 routers, and end hosts. In such a case, multiple Level 1-2 border routers advertise the Level 1 area prefix into the backbone area, even though any one router can reach only a subset of the end hosts in the Level 1 area.
When enabled, the partition avoidance command prevents this partitioning by causing the border router to stop advertising the Level 1 area prefix into the Level 2 backbone. This command displays the output from different areas as a string or additional white space.
Other cases of connectivity loss within the Level 1 area itself are not detected or corrected by the border router, and this command will have no effect.
Examples
The following example causes the routing process named Finance to stop advertising the prefix for the area named area1 when the router no longer has any active adjacencies to area1:
router isis Financepartition avoidance area1Related Commands
is-type
Configures the routing level for an instance of the IS-IS routing process.
Enables the IS-IS routing protocol and specifies an IS-IS process.
passive-interface
To disable sending routing updates on an interface, use the passive-interface command in router configuration mode. To reenable the sending of routing updates, use the no form of this command.
passive-interface [default] {interface-type interface-number}
no passive-interface interface-type interface-number
Syntax Description
default
(Optional) All interfaces become passive.
interface-type
Interface type.
interface-number
Interface number.
Defaults
Routing updates are sent on the interface.
Command Modes
Router configuration
Command History
Usage Guidelines
If you disable the sending of routing updates on an interface, the particular subnet will continue to be advertised to other interfaces, and updates from other routers on that interface continue to be received and processed.
The default keyword sets all interfaces as passive by default. You can then configure individual interfaces where adjacencies are desired using the no passive-interface command. The default keyword is useful in Internet service provider (ISP) and large enterprise networks where many of the distribution routers have more than 200 interfaces.
For the Open Shortest Path First (OSPF) protocol, OSPF routing information is neither sent nor received through the specified router interface. The specified interface address appears as a stub network in the OSPF domain.
For the Intermediate System-to-Intermediate System (IS-IS) protocol, this command instructs IS-IS to advertise the IP addresses for the specified interface without actually running IS-IS on that interface. The no form of this command for IS-IS disables advertising IP addresses for the specified address.
Note
For IS-IS you must keep at least one active interface and configure the interface with the ip router isis command.
Enhanced Interior Gateway Routing Protocol (EIGRP) is disabled on an interface that is configured as passive although it advertises the route.
Examples
The following example sends EIGRP updates to all interfaces on network 10.108.0.0 except Ethernet interface 1:
router eigrp 109network 10.108.0.0passive-interface ethernet 1The following configuration enables IS-IS on Ethernet interface 1 and serial interface 0 and advertises the IP addresses of Ethernet interface 0 in its link-state protocol data units (PDUs):
router isis Financepassive-interface Ethernet 0interface Ethernet 1ip router isis Financeinterface serial 0ip router isis FinanceThe following example sets all interfaces as passive, then activates Ethernet interface 0:
router ospf 100passive-interface defaultno passive-interface ethernet0network 10.108.0.1 0.0.0.255 area 0prc-interval
To customize IS-IS throttling of partial route calculations (PRC), use the prc-interval command in router configuration mode. To restore default values, use the no form of this command.
prc-interval prc-max-wait [prc-initial-wait prc-second-wait]
no prc-interval
Syntax Description
Defaults
prc-max-wait: 5 seconds
prc-initial-wait: 2000 milliseconds
prc-second-wait: 5000 millisecondsCommand Modes
Router configuration
Command History
Usage Guidelines
PRC is the software's process of calculating routes without performing an SPF calculation. This is possible when the topology of the routing system itself has not changed, but a change is detected in the information announced by a particular IS or when it is necessary to attempt to reinstall such routes in the RIB.
The following description will help you determine whether to change the default values of this command:
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•
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Examples
The following example configures intervals for SPF calculations, PRC, and LSP generation:
router isisspf-interval 5 10 20prc-interval 5 10 20lsp-gen-interval 2 50 100redistribute (BGP to ISO IS-IS)
To redistribute routes from a Border Gateway Protocol (BGP) autonomous system into an International Organization for Standardization (ISO) Intermediate System-to-Intermediate System (IS-IS) routing process, use the redistribute command in router configuration mode. To remove the redistribute command from the configuration file and restore the system to its default condition where the software does not redistribute routes, use the no form of this command.
redistribute protocol as-number [route-type] [route-map map-tag]
no redistribute protocol as-number [route-type] [route-map map-tag]
Syntax Description
Defaults
Route redistribution is disabled.
protocol: No source protocol is defined.
route-type: ip
route-map map-tag: If the route-map argument is not entered, all routes are redistributed; if no
map-tag value is entered, no routes are imported.Command Modes
Router configuration
Command History
Usage Guidelines
The clns keyword must be specified to redistribute NSAP prefix routes from BGP into an ISO IS-IS routing process. This version of the redistribute command is used only under router configuration mode for IS-IS processes.
Examples
The following example configures NSAP prefix routes from BGP autonomous system 64500 to be redistributed into the IS-IS routing process called osi-proc-17:
router isis osi-proc-17redistribute bgp 64500 clnsRelated Commands
redistribute (IP)
To redistribute routes from one routing domain into another routing domain, use the redistribute command in router configuration mode. To disable redistribution, use the no form of this command.
redistribute protocol [process-id] {level-1 | level-1-2 | level-2} [as-number] [metric {metric-value | transparent}] [metric-type type-value] [match {internal | external 1 | external 2}]
[tag tag-value] [route-map map-tag] [subnets]no redistribute protocol [process-id] {level-1 | level-1-2 | level-2} [as-number] [metric {metric-value | transparent}] [metric-type type-value] [match {internal | external 1 | external 2}] [tag tag-value] [route-map map-tag] [subnets]
Syntax Description
Command Default
Route redistribution is disabled.
protocol: No source protocol is defined.
process-id: No process ID is defined.
metric metric-value: 0
metric-type type-value: Type 2 external route
match internal | external: Internal, external 1, external 2
external: Internal
tag tag-value: If no value is specified, the remote autonomous system number is used for routes from BGP and EGP; for other protocols, the default is 0.
route-map map-tag: If the route-map keyword is not entered, all routes are redistributed; if no map-tag value is entered, no routes are imported.
subnets: No subnets are defined.Command Modes
Router configuration
Address family configurationCommand History
Usage Guidelines
Changing or disabling any keyword will not affect the state of other keywords.
A router receiving a link-state protocol with an internal metric will consider the cost of the route from itself to the redistributing router plus the advertised cost to reach the destination. An external metric only considers the advertised metric to reach the destination.
Routes learned from IP routing protocols can be redistributed at Level 1 into an attached area or at Level 2. The level-1-2 keyword allows both Level 1 and Level 2 routes in a single command.
Redistributed routing information must be filtered by the distribute-list out router configuration command. This guideline ensures that only those routes intended by the administrator are passed along to the receiving routing protocol.
Whenever you use the redistribute or the default-information router configuration commands to redistribute routes into an OSPF routing domain, the router automatically becomes an ASBR. However, an ASBR does not, by default, generate a default route into the OSPF routing domain.
When routes are redistributed into OSPF from protocols other than OSPF or BGP, and no metric has been specified with the metric-type keyword and type-value argument, OSPF will use 20 as the default metric. When routes are redistributed into OSPF from BGP, OSPF will use 1 as the default metric. When routes are redistributed from one OSPF process to another OSPF process, Autonomous system (AS) external and not-so-stubby-area (NSSA) routes will use 20 as the default metric. When intra-area and inter-area routes are redistributed between OSPF processes, the internal OSPF metric from the redistribution source process is advertised as the external metric in the redistribution destination process. (This is the only case in which the routing table metric will be preserved when routes are redistributed into OSPF.)
When routes are redistributed into OSPF, only routes that are not subnetted are redistributed if the subnets keyword is not specified.
Routes configured with the connected keyword affected by this redistribute command are the routes not specified by the network router configuration command.
You cannot use the default-metric command to affect the metric used to advertise connected routes.
Note
Default redistribution of IGPs or EGP into BGP is not allowed unless the default-information originate router configuration command is specified.
Examples
The following example shows how OSPF routes are redistributed into a BGP domain:
router bgp 109redistribute ospfThe following example causes Enhanced Interior Gateway Routing Protocol (EIGRP) routes to be redistributed into an OSPF domain:
router ospf 110redistribute eigrpThe following example causes the specified EIGRP process routes to be redistributed into an OSPF domain. The EIGRP-derived metric will be remapped to 100 and RIP routes to 200.
router ospf 109redistribute eigrp 108 metric 100 subnetsredistribute rip metric 200 subnetsThe following example configures BGP routes to be redistributed into IS-IS. The link-state cost is specified as 5, and the metric type will be set to external, indicating that it has lower priority than internal metrics.
router isisredistribute bgp 120 metric 5 metric-type externalIn the following example, network 172.16.0.0 will appear as an external link-state advertisement (LSA) in OSPF 1 with a cost of 100 (the cost is preserved):
interface ethernet 0ip address 172.16.0.1 255.0.0.0ip ospf cost 100interface ethernet 1ip address 10.0.0.1 255.0.0.0!router ospf 1network 10.0.0.0 0.255.255.255 area 0redistribute ospf 2 subnetrouter ospf 2network 172.16.0.0 0.255.255.255 area 0Related Commands
redistribute (ISO ISIS to BGP)
To redistribute routes from an International Organization for Standardization (ISO) Intermediate System-to-Intermediate System (IS-IS) routing process into a Border Gateway Protocol (BGP) autonomous system, use the redistribute command in router configuration mode. To remove the redistribute command from the configuration file and restore the system to its default condition where the software does not redistribute routes, use the no form of this command.
redistribute protocol [process-id] [route-type] [route-map map-tag]
no redistribute protocol [process-id] [route-type] [route-map map-tag]
Syntax Description
Defaults
Route redistribution is disabled.
protocol: No source protocol is defined.
route-type: ip
route-map map-tag: If the route-map argument is not entered, all routes are redistributed; if no
map-tag value is entered, no routes are imported.Command Modes
Router configuration
Command History
Usage Guidelines
The clns keyword must be specified to redistribute NSAP prefix routes from an ISO IS-IS routing process into BGP. This version of the redistribute command is used only under router configuration mode for BGP processes.
Examples
The following example configures CLNS NSAP routes from the IS-IS routing process called osi-proc-6 to be redistributed into BGP:
router bgp 64352redistribute isis osi-proc-6 clnsRelated Commands
redistribute dvmrp
To configure redistribution of Distance Vector Multicast Routing Protocol (DVMRP) routes into multiprotocol BGP, use the redistribute dvmrp command in address family or router configuration mode. To stop such redistribution, use the no form of this command.
redistribute dvmrp [route-map map-name]
no redistribute dvmrp [route-map map-name]
Syntax Description
Defaults
DVMRP routes are not redistributed into multiprotocol BGP.
Command Modes
Address family configuration
Router configuration
Command History
11.1(20)CC
This command was introduced.
12.0(7)T
Address family configuration mode was added.
Usage Guidelines
Use this command if you have a subset of DVMRP routes in an autonomous system that you want to take the multiprotocol BGP path. Define a route map to further specify which DVMRP routes get redistributed.
Examples
The following router configuration mode example redistributes DVMRP routes to BGP peers that match access list 1:
router bgp 109redistribute dvmrp route-map dvmrp-into-mbgproute-map dvmrp-into-mbgpmatch ip address 1The following address family configuration mode example redistributes DVMRP routes to multiprotocol BGP peers that match access list 1:
router bgp 109address-family ipv4 multicastredistribute dvmrp route-map dvmrp-into-mbgproute-map dvmrp-into-mbgpmatch ip address 1route-map (IP)
To define the conditions for redistributing routes from one routing protocol into another, or to enable policy routing, use the route-map command in global configuration mode and the match and set command in route-map configuration modes. To delete an entry, use the no form of this command.
route-map map-tag [permit | deny] [sequence-number]
no route-map map-tag [permit | deny] [sequence-number]
Syntax Description
Defaults
No default is available.
Command Modes
Global configuration
Command History
Usage Guidelines
Use route maps to redistribute routes or to subject packets to policy routing. Both purposes are described in this section.
Redistribution
Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route-map command. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.
The match route-map configuration command has multiple formats. The match commands can be given in any order, and all match commands must "pass" to cause the route to be redistributed according to the set actions given with the set commands. The no forms of the match commands remove the specified match criteria.
Use route maps when you want detailed control over how routes are redistributed between routing processes. The destination routing protocol is the one you specify with the router global configuration command. The source routing protocol is the one you specify with the redistribute router configuration command. See the "Examples" section for an illustration of how route maps are configured.
When you are passing routes through a route map, a route map can have several parts. Any route that does not match at least one match clause relating to a route-map command will be ignored; that is, the route will not be advertised for outbound route maps and will not be accepted for inbound route maps. If you want to modify only some data, you must configure a second route map section with an explicit match specified.
Policy Routing
Another purpose of route maps is to enable policy routing. Use the ip policy route-map command, in addition to the route-map command, and the match and set commands to define the conditions for policy routing packets. The match commands specify the conditions under which policy routing occurs. The set commands specify the routing actions to perform if the criteria enforced by the match commands are met. You might want to policy route packets some way other than the obvious shortest path.
The sequence-number argument works as follows:
1.
2.
3.
If the no route-map map-tag command is specified (with no sequence-number argument), the whole route map is deleted.
Examples
The following example redistributes Routing Information Protocol (RIP) routes with a hop count equal to 1 into Open Shortest Path First (OSPF). These routes will be redistributed into OSPF as external link-state advertisements (LSAs) with a metric of 5, metric type of Type 1, and a tag equal to 1.
router ospf 109redistribute rip route-map rip-to-ospfroute-map rip-to-ospf permitmatch metric 1set metric 5set metric-type type1set tag 1Related Commands
router bgp
To configure the BGP routing process, use the router bgp command in global configuration mode. To remove a routing process, use the no form of this command.
router bgp as-number
no router bgp as-number
Syntax Description
as-number
Number of an autonomous system that identifies the router to other BGP routers and tags the routing information passed along.
Defaults
No BGP routing process is enabled by default.
Command Modes
Global configuration
Command History
Usage Guidelines
This command allows you to set up a distributed routing core that automatically guarantees the loop-free exchange of routing information between autonomous systems.
Examples
The following example configures a BGP process for autonomous system 120:
router bgp 120Related Commands
Specifies the list of networks for the BGP routing process.
Adjusts BGP network timers.
router eigrp
To configure the Enhanced Interior Gateway Routing Protocol (EIGRP) process, use the router eigrp command in global configuration mode. To shut down a routing process, use the no form of this command.
router eigrp as-number
no router eigrp as-number
Syntax Description
as-number
Autonomous system number that identifies the routes to the other EIGRP routers. It is also used to tag the routing information.
Defaults
This command is disabled by default.
Command Modes
Global configuration
Command History
Examples
The following example configures an EIGRP routing process and assigns process number 109:
router eigrp 109Related Commands
