EIGRP allows for up to six equal-metric routes to be installed into the IP routing table at the same time. However, because of the complex EIGRP metric calculation, metrics may often be close to each other, but not exactly equal. To allow for metrics that are somewhat close in value to be considered equal, and added to the IP routing table, you can use the variance multiplier command. The multiplier defines a value that is multiplied by the lowest metric (in other words, the ..
BGP neighbor relationships, often called peering, are usually manually configured into routers by the network administrator, according to certain rules and to logically follow the overall network topology. Each neighbor session runs over TCP (port 179) to ensure reliable delivery and incremental, rather than periodic, rebroadcasting of updates. These two characteristics distinguish BGP from the auto-neighbor-discover/periodic-rebroadcast nature of most interior routing protoc..
MPLS Control- and Forwarding-Plane Components
Even though IP and MPLS forwarding schemes are quite different, the two are similar in many ways. For example, conventional IP routers forward packets by looking up the IP destination address in the Forwarding Information Base (FIB). In contrast, a label-switching router (LSR) makes its forwarding decision by performing a label lookup in the Label Forwarding Information Base (LFIB). The forwarding state in the FIB is derived from the routing information distributed by IP con..
To enable locally administered user IDs, use the following set of configuration commands: Router1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router1(config)#username ijbrown password oreilly Router1(config)#username kdooley password cookbook Router1(config)#aaa new-model Router1(config)#aaa authentication login local_auth local Router1(config)#line vty 0 4 Router1(config-line)#login authentication local_auth Router1(config-line)#exi..
OSPF authentication causes routers to authenticate every OSPF message. To do so, the routers use the same preshared key value, generating an MD5 digest for each OSPF message and sending that digest as part of each OSPF message. If a router configured for OSPF authentication receives an OSPF message, and the received message’s MD5 digest does not pass the authentication checking based on the local key value, the router silently discards the message. As a result, when a..
