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n this chapter, we will discuss how to take networks running dif-
ferent routing protocols and allow them to exchange routing information,
through a process called route redistribution. One of the challenges of route
redistribution is that many routing protocols use different metrics. To over-
come this challenge, we will show you how to set default metrics for various
routing protocols. After examining several redistribution examples, we will
review commands for verifying and troubleshooting route redistribution.
We will discuss many advanced route-manipulation techniques, including
setting metrics on a protocol-by-protocol basis and setting metrics for spe-
cific routes. We'll introduce the distribute-list feature as a tool for fil-
tering the receiving or advertising of routes, and we'll show the virtual
interface Null0 to be an efficient way of discarding packets destined for spec-
ified networks. We will also detail how to redistribute static and connected
routes. In addition, we'll introduce the powerful features of route maps.
Route Redistribution
e have previously discussed various routing protocols available on
Cisco routers. Some of the more common routing protocols are RIP, IGRP,
EIGRP, and OSPF. However, we have not considered what happens when
we interconnect networks that are running differing routing protocols. To
illustrate this situation, let's consider the implications of when two busi-
nesses (or divisions within the same business) merge. Let's say that Company
A had a network infrastructure that used the Cisco proprietary EIGRP pro-
tocol, as shown in Figure 10.1.
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