It is quite common to find yourself in the position of needing to manage two routing protocols within the same network. This can be due to a merger between two companies or because you are migrating from one protocol to another. EIGRP has built-in mechanisms that allow you to easily translate route information from one protocol to another.

In the example that follows, we have two companies that are merging. In this instance, the new company is running OSPF and we need to insert routes from our EIGRP network into their network. We also need to receive route information from the OSPF process. However, there are certain routes that we do not want to inject into their network. We will use a route filter to prevent these routes from being propagated. Figure 2.25 show the two networks and the link used to connect them.

Figure 2.25: Redistributing between EIGRP and OSPF

We will focus our attention on Router E. It will function both as an EIGRP Core router and an OSPF ASBR (Autonomous System Boundary Router), and we can control the redistribution process entirely from there. The first objective is to modify the original EIGRP-only configuration at Router E to add it to the OSPF 10 process. The original OSPF network is using the address space 10.31.0.0/16. We could enable OSPF on Router E using 10.0.0.0, but that would prevent us from ever using the 10.0.0.0 address space anywhere else in our network. Therefore, the...