that was running EIGRP and OSPF, and you needed the routes learned by EIGRP to be advertised in OSPF, you would redistribute the EIGRP routes into OSPF. Another common example is the re- distribution of static or connected routes. Because static routes are entered manually, and not learned, they must be redistributed into a routing protocol if you wish them to be advertised. As Figure 11-1 shows, routes learned through EIGRP are not automatically advertised out of the OSPF interfaces. To accomplish this translation of sorts, you must configure redistribution within the protocol where you wish the routes to appear. EIGRP 100 OSPF 100 10.10.10.0/24 10.20.20.0/24 NOT advertised via OSPF 50.50.50.0/24 Learned via EIGRP Figure 11-1. Most routing protocols do not redistribute by default One of the main reasons protocols do not redistribute routes automatically is that dif- ferent protocols have vastly different metrics. OSPF, for example, calculates the best route based on the bandwidth of the links. EIGRP, on the other hand, uses bandwidth and delay (by default) to form a very different metric. While the router could assume you wanted to redistribute, and assign a standard metric to the learned routes, a better approach is to allow you to decide whether and how routes should be redistributed. There are two steps to redistributing routes. First, you must configure a metric. This allows the routing protocol to assign a metric that it understands to the incoming routes. Second, add the redistribute command. The exact commands used for these purposes vary widely between protocols, and they'll be discussed individually in the sections that follow. One reason to redistribute routes might be the inclusion of a firewall that must partic- ipate in dynamic routing but cannot use the protocol in use on the network. For ex- ample, many firewalls support RIP, but not EIGRP. To dynamically route between an EIGRP router and a RIP-only firewall, you must redistribute between RIP and EIGRP on the router. The best rule to remember when