Easily control route redistribution using a route-map

Route map are useful to control route redistribution into OSPF, EIGRP or any other routing protocol.

Let's start with an example : allow redistribution of all static route except those which are tagged with the number '8'

!
router ospf 1
redistribute static subnets route-map STATIC
! ......
!
ip route 10.10.1.0 255.255.255.0 10.10.0.1 tag 8
ip route 10.20.45.0 255.255.255.0 10.10.0.3
!
route-map STATIC deny 10
match tag 8
!
route-map STATIC permit 20
!

10.20.45.0 will be redistributed in OSPF1, 10.10.1.0 will not. As you can see, this route-map uses an ACL syntax to match the routes.

Available match statements :

match interface : select outgoing interface
match ip address : select based on ip address (ACL or prefix-list)
match ip next-hop : select based on route next-hop
match metric : select based on route metric
match ip source-route : select based on LSA router-id originator
match route-type : select based on E1 or E2 route type (external 1 or external 2)
match tag : see example above.

You can also change some route properties, on the fly, like in this example :

!
router ospf 1
redistribute static subnets route-map STATIC
! ......
!
ip route 10.10.1.0 255.255.255.0 10.10.0.1 tag 8
ip route 10.20.45.0 255.255.255.0 10.10.0.3
!
route-map STATIC deny 10
match tag 8
!
route-map STATIC permit 20
set tag 9
!

All redistributed route (which had a 8 tag) will now have tag 9.

Available set statements :

set as-path : set BGP as-path

set community : set BPG community
set ip next-hop : set BGP next-hop
set level : set which level (l1, l2, stub, backbone) a matching route should be
set local-preference : set BGP local preference for matching route to exit the current AS
set metric : set route metric
set nlri : set BGP nlri (choose which BGP table a matching route should go)
set origin : set BGP origin
set tag : set a new tag (see example above)
set weight : set BGP route weight