Redistribution Tips

07 May 2011 - Lab-Rat

Protocol Specific Configuration Notes

• OSPF - use the subnets command. If a metric not specified, OSPF sets it to 20, except for BGP, which get set to 1.
• EIGRP - specify a metric for the redistributed routes, or use the default-metric command. 10000 100 255 100 1500 works fine. Good idea to add no auto-summary if allowed.
• RIP - specify a metric for the redistributed routes, or use the default-metric command. 2 works fine. Also be sure to use version 2 to support classless.

Route Tagging Example

Use Route Filtering to prevent feedback loops can be done with distribute lists, or more elegantly through route maps. The simple rule is never redistribute routes from a protocol back into itself. Here’s an example:

router eigrp-123
redistribute ospf 1 route-map OSPF2EIGRP
default-metric 10000 100 255 100 1500
no auto-summary

router ospf 1
redistribute eigrp 123 subnets route-map EIGRP2OSPF

route-map OSPF2EIGRP deny 10
!Deny any routes originated from EIGRP
match tag 90
route-map OSPF2EIGRP permit 20
!Mark these routes as from OSPF
set tag 110

route-map EIGRP2OSPF deny 10
!Deny any routes originated from OSPF
match tag 110
route-map EIGRP2OSPF permit 20
!Mark these routes from EIGRP
set tag 90

You can see the tags by doing a “show ip route x.x.x.x”, where x.x.x.x is the target route.

Redistributing Routing Protocols