I hope this example will make U understand how to configure this tricky command:
I would like to advertise a default route of 9.9.9.99 to every eigrp router: First create a default static route with the classfull network U are trying to advertise: There are two methods for creating this static route: One is using the #ip default-network 9.9.9.9 command Which will create a static route for you. Another method is by creating the static route by yourself. BB2#configure terminal Enter configuration commands, one per line. End with CNTL/Z. BB2(config)#ip route 9.0.0.0 255.0.0.0 9.9.9.99 BB2(config)#end BB2#sh *Jun 22 21:42:42.851: %SYS-5-CONFIG_I: Configured from console by console BB2#sh ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, + - replicated route Gateway of last resort is not set 10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks C 10.0.0.0/24 is directly connected, FastEthernet0/0 L 10.0.0.1/32 is directly connected, FastEthernet0/0 C 10.10.10.0/24 is directly connected, FastEthernet0/0 L 10.10.10.1/32 is directly connected, FastEthernet0/0 BB2# As U can see this static route is not in the routing table. Because we don;t have a connected interface in this subnet. Now let;s add one: BB2(config-if)#ip address 9.9.9.9 *Jun 22 21:44:41.251: %LINK-3-UPDOWN: Interface Loopback1, changed state to up *Jun 22 21:44:42.251: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback1, changed state to up BB2(config-if)#ip address 9.9.9.9 255.255.255.0 BB2(config-if)#end BB2# *Jun 22 21:44:48.771: %SYS-5-CONFIG_I: Configured from console by console BB2#sh ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, + - replicated route Gateway of last resort is not set 9.0.0.0/8 is variably subnetted, 3 subnets, 3 masks S 9.0.0.0/8 [1/0] via 9.9.9.99 C 9.9.9.0/24 is directly connected, Loopback1 L 9.9.9.9/32 is directly connected, Loopback1 As U can see, now we have this static route in the routing table. Now let;s mark this one as a candidate default route: The following command will ONLY work if we have a static route in the routing table (created with another ip default-network command or with ip route command) Why? Ask CISCO ! BB2(config)#ip default-network 9.0.0.0 BB2(config)#end BB2#sh i *Jun 22 21:46:03.119: %SYS-5-CONFIG_I: Configured from console by console BB2#sh ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, + - replicated route Gateway of last resort is 9.9.9.99 to network 9.0.0.0 S* 0.0.0.0/0 [1/0] via 9.9.9.99 * 9.0.0.0/8 is variably subnetted, 3 subnets, 3 masks S* 9.0.0.0/8 [1/0] via 9.9.9.99 C 9.9.9.0/24 is directly connected, Loopback1 L 9.9.9.9/32 is directly connected, Loopback1 Now this route is a default route for us, let;s make a check on eigrp neighbor BB1: BB1#sh ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, + - replicated route Gateway of last resort is not set 10.0.0.0/8 is variably subnetted, 3 subnets, 2 masks C 10.0.0.0/24 is directly connected, FastEthernet0/0 L 10.0.0.2/32 is directly connected, FastEthernet0/0 D 10.10.10.0/24 [90/30720] via 10.0.0.1, 00:54:29, FastEthernet0/0 This router is not having a default candidate yet. For this to happen, we need to advertise this static route from BB2, which is a default candidate for BB2 only now, into eigrp, using redistribute static: BB2(config)#router eigrp 1 BB2(config-router)#redistribute static And now let's check the routing table on BB1: BB1#sh ip route Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2 i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2 ia - IS-IS inter area, * - candidate default, U - per-user static route o - ODR, P - periodic downloaded static route, + - replicated route Gateway of last resort is not set D*EX 9.0.0.0/8 [170/156160] via 10.0.0.1, 00:01:04, FastEthernet0/0 Voila, this route is here, marked as a default candidate route. Hope this clarified everything about the usage of this command. _______________________________________________ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com
