31 Days Before Your CCNA Exam

218 31 Days Before Your CCNA ExamExample 13-6Larger Routing Table on R2R2#sh ip routeGateway of last resort is not setDDDD192.168.0.0/24 [90/2297856] via 192.168.10.10, 00:01:20, Serial0/0/1192.168.1.0/24 [90/2172416] via 192.168.10.10, 00:04:45, Serial0/0/1192.168.2.0/24 [90/2297856] via 192.168.10.10, 00:01:18, Serial0/0/1192.168.3.0/24 [90/2297856] via 192.168.10.10, 00:01:16, Serial0/0/1The routes in Example 13-6 can be summarized into one supernet route advertised by R3 to bothR1 and R2. A supernet is a collection of contiguous classful network addresses aggregated into oneroute. Instead of sending four /24 routes for the classful networks 192.168.0.0, 192.168.1.0,192.168.2.0, and 192.168.3.0, we can configure a manual summary route as 192.168.0.0/22.Manual summary routes must be configured on the interface that you want the summary route tobe sent out of. The syntax for manual summary routes with EIGRP is as follows:Router(config-if)#ip summary-address eigrp as-number network-address subnet-maskBecause R3 has two EIGRP neighbors, the EIGRP manual summarization in configured on bothSerial 0/0/0 and Serial 0/0/1, as shown in Example 13-7.Example 13-7Configuring Manual Summary Routes for EIGRPR3(config)#interface serial 0/0/0R3(config-if)#ip summary-address eigrp 1 192.168.0.0 255.255.252.0R3(config-if)#interface serial 0/0/1R3(config-if)#ip summary-address eigrp 1 192.168.0.0 255.255.252.0R1 and R2 now have smaller routing tables because the four networks are summarized into oneroute, as highlighted in Example 13-8 for R2.Example 13-8Smaller Routing Table for R2R2#show ip routeGateway of last resort is not setDCDCCCD192.168.10.0/30 is subnetted, 2 subnets192.168.10.4 [90/2681856] via 192.168.10.10, 00:01:11, Serial0/0/1[90/2681856] via 172.16.3.1, 00:00:06, Serial0/0/0192.168.10.8 is directly connected, Serial0/0/1172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks172.16.1.0/24 [90/2172416] via 172.16.3.1, 00:00:06, Serial0/0/0172.16.2.0/24 is directly connected, FastEthernet0/0172.16.3.0/30 is directly connected, Serial0/0/010.0.0.0/30 is subnetted, 1 subnets10.1.1.0 is directly connected, Loopback1192.168.0.0 [90/2681856] via 192.168.10.10, 00:01:11, Serial0/0/1