Troubleshoot Routing Redistribution

Exam: Cisco 642-832 - Troubleshooting and Maintaining Cisco IP Networks (TSHOOT v1.0)

Route redistribution involves sending routes from one routing protocol into another routing protocol.

To troubleshoot redistribution, if a redistributed route does not appear in the routing table:

• Make sure that the same route is not being adevertised by another routing protocol which has a lower administrative distance. For instance, if you are redistributing 10.1.1.0/24 into EIGRP from BGP and a static 10.1.1.0/24 is already present in your router then you will not see the redistributed route in your router since static route has lower administrative distance than EIGRP routes. You can use the "sh ip route [PREFIX]" command to check which route is actually present in the routing table.
• The route you want to redistribute must be present in the routing table of the redistributing router. This is very important when redistributing between two dynamic routing protocols. Because, you recieve route from one protocol and redistribute into another so it must be ensured the route is being recieved before you can redistribute it.
• Its always recommended to use router filters in redistribution. Make sure that the redistributed route has a matching statement in the prefix-list or access-list. The subnet mask in the prefix-list must match the route present in the routing table.
• Note that the route metrics are lost when redistributing between protocols so its always recommended to set metric of redistributed routes. EIGRP routes are not redistributed if no metrics are specified, so the metrics must be specificed with the 'metric' command when redistributing into EIGRP.
• For OSPF, only classful subnets are redistributed unless you use the 'subnet' keyword with the redistribution command.