Advanced OSPF Design Concepts

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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 related match and set commands are listed in the section “Related Commands for Policy Routing.” 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.

Example 1: The following example redistributes all OSPF routes into IGRP:

    router igrp 109    redistribute ospf 110    default metric 1000 100 255 1 1500 

Example 2: The following example redistributes RIP routes with a hop count equal to 1 into OSPF. These routes will be redistributed into OSPF as external LSAs with a metric of 5, metric type of Type 1 and a tag equal to 1:

    router ospf 109    redistribute rip route-map rip-to-ospf    route-map rip-to-ospf permit    match metric 1    set metric 5    set metric-type type1    set tag 1 

Related Commands for Redistribution:

match as-path	set automatic-tag
match community-list	set community
match interface	set level
match ip address	set local-preference
match ip next-hop	set metric
match ip route-source	set metric-type
match metric	set next-hop
match route-type	set origin
match tag	set tag
set as-path	set weight
show route-map

Related Commands for Policy Routing

ip policy route-map	set interface
match ip address	set ip default next-hop
match length	set ip next-hop
set default interface

router ospf

To configure an OSPF routing process, use the router ospf global configuration command. To terminate an OSPF routing process, use the no form of this command. The syntax for this command (and the no form) is as follows:

    router ospf process-id    no router ospf process-id 

Syntax Description:

process-id. Internally used identification parameter for an OSPF routing process. It is locally assigned and can be any positive integer. A unique value is assigned for each OSPF routing process.

Default: No OSPF routing process is defined.

Command Mode: Global configuration.

Usage Guidelines: You can specify multiple OSPF routing processes in each router.

Example: The following example shows how to configure an OSPF routing process and assign a process number of 109:

    router ospf 109 

Related Commands: network area

set level

To indicate where to import routes, use the set level route map configuration command. To delete an entry, use the no form of this command. The syntax for this command (and the no form) is as follows:

    set level {level-1 | level-2 | level-1-2 | stub-area | backbone}    no set level {level-1 | level-2 | level-1-2 | stub-area | backbone} 

Syntax Description:

level-1. Imports routes into a Level-1 area.

level-2. Imports routes into Level-2 subdomain.

level-1-2. Imports routes into Level-1 and Level-2.

stub-area. Imports routes into OSPF NSSA area.

backbone. Imports routes into OSPF backbone area.

set metric

To set the metric value for the destination routing protocol, use the set metric route map configuration command. To return to the default metric value, use the no form of this command. The syntax for this command (and the no form) is as follows:

    set metric metric-value    no set metric metric-value 

Syntax Description:

metric-value. Metric value or IGRP bandwidth in kilobits per second. It can be an integer from -294,967,295 through 294,967,295.

Default: Default metric value.

Command Mode: Route map configuration.

Usage Guidelines: Use the route-map global configuration command, and the match and set route-map configuration commands, to define the conditions for redistributing routes from one routing protocol into another. Each route-map command has a list of match and set commands associated with it. The match commands specify the match criteria—the conditions under which redistribution is allowed for the current route map. The set commands specify the set actions—the particular redistribution actions to perform if the criteria enforced by the match commands are met. The no route-map command deletes the route map.

The set route-map configuration commands specify the redistribution set actions to be performed when all of a route map’s match criteria are met. When all match criteria are met, all set actions are performed.

Example: In the following example, the metric value for the destination routing protocol is set to 100:

    route-map set-metric    set metric 100 

Related Commands:

match as-path	set as-path
match community-list	set automatic-tag
match interface	set community
match ip address	set level
match ip next-hop	set local-preference
match ip route-source	set metric-type
match metric	set next-hop
match route-type	set origin
match tag	set tag
route-map	set weight

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