stance of 170, and are marked with the letters D EX at the beginning of the route: R3# sho ip route [text removed] Gateway of last resort is 192.168.1.2 to network 0.0.0.0 5.0.0.0/32 is subnetted, 1 subnets D EX 5.5.5.5 [170/409600] via 10.10.10.5, 00:00:03, Etherneto/o 10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks 10.10.10.0/24 is directly connected, Etherneto/o 10.100.100.100/32 is directly connected, Loopback0 192.168.1.0/24 is directly connected, Ethernet1/0 192.168.3.0/24 [90/2195456] via 10.10.10.5, 00:08:42, Etherneto/o 0.0.0.0/0 [254/0] via 192.168.1.2 EIGRP stores its information in three databases: the route database, the topology database, and the neighbor database. Viewing the topology database can be a tre- mendous help when troubleshooting routing problems. Not only can you see what EIGRP has put into the routing table, but you can also see what EIGRP considers to be alternate possibilities for routes: R3# sho ip eigrp topology IP-EIGRP Topology Table for AS(100)/ID(10.100.100.100) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, S - sia Status P 5.5.5.5/32, 1 successors, FD is 409600 via 10.10.10.5 (409600/128256), Etherneto/o P 10.10.10.0/24, 1 successors, FD is 281600 via Connected, Etherneto/o P 192.168.3.0/24, 1 successors, FD is 2195456 via 10.10.10.5 (2195456/2169856), Etherneto/o Chapter 10: Routing Protocols In a nutshell, the premise of the Open Shortest Path First (OSPF) routing protocol is that the shortest or fastest path that is available is the one that will be used. OSPF is the routing protocol of choice when: There are routers from vendors other than Cisco in the network. The network requires segmentation into areas or zones. There is a desire to avoid proprietary protocols. OSPF is a link-state routing protocol. The metric it uses is bandwidth. The band- width of each link is calculated using the formula 100,000,000 divided by the bandwidth of the link in bps. Thus, a 100 Mbps link has a metric or "cost" of 1, a 10 Mbps link has a cost of 1