Implementing Cisco Networking Solutions

Route redistribution

We have discussed multiple ways of building a routing table using different protocols such as static routing, RIP, OSPF, and IS-IS. Although each type of protocol creates entries in a routing table for the prefixes in the domains that run the specific protocols, the protocols do not, however, take the routes from the routing table that were populated by other means and advertise them. As an example, consider the upcoming figure, where we use static routing within one domain of the network and OSPF in another domain.

The routing table for router RA would have the prefixes in the network 10.0.0.0/21 from domain A as they are learned by OSPF. Router RA also has a static router pointed toward router RD for the prefix 10.0.12.0/23 ...