如下图示：
R1: interface Loopback0 ip address 1.1.1.1 255.255.255.255 interface FastEthernet0/0 ip address 12.1.1.1 255.255.255.0 no sh interface FastEthernet0/1 ip address 13.1.1.1 255.255.255.0 no sh router bgp 65001 bgp router-id 1.1.1.1 bgp confederation identifier 100 //联邦AS号 bgp confederation peers 65002 //如果不加peers的话，65001学习不到同为联邦的AS 65002子路由。 network 1.1.1.1 mask 255.255.255.255 neighbor 12.1.1.2 remote-as 200 neighbor 13.1.1.3 remote-as 65002 neighbor 13.1.1.3 next-hop-self R2: interface Loopback0 ip address 2.2.2.2 255.255.255.255 interface FastEthernet0/0 ip address 12.1.1.2 255.255.255.0 no sh interface FastEthernet1/0 ip address 23.1.1.2 255.255.255.0 no sh router bgp 200 bgp router-id 2.2.2.2 network 2.2.2.2 mask 255.255.255.255 network 12.1.1.0 mask 255.255.255.0 //需要宣告所有互连网络的eBGP网段，才能互通R4的路由。 network 23.1.1.0 mask 255.255.255.0 //同上。 neighbor 12.1.1.1 remote-as 100 neighbor 23.1.1.3 remote-as 100 R3: interface Loopback0 ip address 3.3.3.3 255.255.255.255 interface FastEthernet0/0 ip address 34.1.1.3 255.255.255.0 no interface FastEthernet0/1 ip address 13.1.1.3 255.255.255.0 no sh interface FastEthernet1/0 ip address 23.1.1.3 255.255.255.0 no sh router eigrp 1 //R3和R4互联IGP路由 network 3.0.0.0 network 34.0.0.0 no auto-summary router bgp 65002 bgp router-id 3.3.3.3 bgp confederation identifier 100 //联邦AS号 bgp confederation peers 65001 //如果不加peers的话，65002学习不到同为联邦的AS 65001子路由。 network 3.3.3.3 mask 255.255.255.255 network 13.1.1.0 mask 255.255.255.0 //需要宣告所有网段路由，才能让各种iBGP和eBGP学习到精确路由，否则会产生路由环，导致网络不通。 network 23.1.1.0 mask 255.255.255.0 //同上 network 34.1.1.0 mask 255.255.255.0 //同上 neighbor 4.4.4.4 remote-as 65002 neighbor 4.4.4.4 update-source Loopback0 neighbor 4.4.4.4 next-hop-self neighbor 13.1.1.1 remote-as 65001 neighbor 13.1.1.1 next-hop-self neighbor 23.1.1.2 remote-as 200 R4: interface Loopback0 ip address 4.4.4.4 255.255.255.255 interface FastEthernet0/0 ip address 34.1.1.4 255.255.255.0 no sh router eigrp 1 //R3和R4互联IGP路由 network 4.0.0.0 network 34.0.0.0 no auto-summary router bgp 65002 bgp router-id 4.4.4.4 network 4.4.4.4 mask 255.255.255.255 network 34.1.1.0 mask 255.255.255.0 //需要宣告本地互连网络到iBGP,才能让iBGP和eBGP学习到相关路由，和去向iBGP和eBGP路由学习。如果不宣告，R2学习不到R4的路由。 neighbor 3.3.3.3 remote-as 65002 neighbor 3.3.3.3 update-source Loopback0
R2#ping 4.4.4.4 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 20/37/56 ms R2# R2# R2#show ip route Codes: 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 Gateway of last resort is not set 34.0.0.0/24 is subnetted, 1 subnets B 34.1.1.0 [20/0] via 23.1.1.3, 00:01:43 1.0.0.0/32 is subnetted, 1 subnets B 1.1.1.1 [20/0] via 12.1.1.1, 00:01:43 2.0.0.0/32 is subnetted, 1 subnets C 2.2.2.2 is directly connected, Loopback0 3.0.0.0/32 is subnetted, 1 subnets B 3.3.3.3 [20/0] via 23.1.1.3, 00:01:43 4.0.0.0/32 is subnetted, 1 subnets B 4.4.4.4 [20/0] via 23.1.1.3, 00:01:43 23.0.0.0/24 is subnetted, 1 subnets C 23.1.1.0 is directly connected, FastEthernet1/0 12.0.0.0/24 is subnetted, 1 subnets C 12.1.1.0 is directly connected, FastEthernet0/0 13.0.0.0/24 is subnetted, 1 subnets B 13.1.1.0 [20/0] via 23.1.1.3, 00:01:46 R4#ping 2.2.2.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 20/30/36 ms R4#show ip route Codes: 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 Gateway of last resort is not set 34.0.0.0/24 is subnetted, 1 subnets C 34.1.1.0 is directly connected, FastEthernet0/0 1.0.0.0/32 is subnetted, 1 subnets B 1.1.1.1 [200/0] via 3.3.3.3, 00:02:47 2.0.0.0/32 is subnetted, 1 subnets B 2.2.2.2 [200/0] via 3.3.3.3, 00:02:47 3.0.0.0/32 is subnetted, 1 subnets D 3.3.3.3 [90/409600] via 34.1.1.3, 00:03:37, FastEthernet0/0 4.0.0.0/32 is subnetted, 1 subnets C 4.4.4.4 is directly connected, Loopback0 23.0.0.0/24 is subnetted, 1 subnets B 23.1.1.0 [200/0] via 3.3.3.3, 00:02:48 12.0.0.0/24 is subnetted, 1 subnets B 12.1.1.0 [200/0] via 3.3.3.3, 00:02:49 13.0.0.0/24 is subnetted, 1 subnets B 13.1.1.0 [200/0] via 3.3.3.3, 00:02:49
R1#show ip bgp all summary For address family: IPv4 Unicast BGP router identifier 1.1.1.1, local AS number 65001 BGP table version is 12, main routing table version 12 8 network entries using 936 bytes of memory 11 path entries using 572 bytes of memory 5/3 BGP path/bestpath attribute entries using 620 bytes of memory 3 BGP AS-PATH entries using 72 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 2200 total bytes of memory BGP activity 8/0 prefixes, 11/0 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 12.1.1.2 4 200 13 11 12 0 0 00:06:08 3 13.1.1.3 4 65002 12 11 12 0 0 00:06:03 7 R2#show ip bgp all summary For address family: IPv4 Unicast BGP router identifier 2.2.2.2, local AS number 200 BGP table version is 9, main routing table version 9 8 network entries using 936 bytes of memory 15 path entries using 780 bytes of memory 4/3 BGP path/bestpath attribute entries using 496 bytes of memory 1 BGP AS-PATH entries using 24 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 2236 total bytes of memory BGP activity 8/0 prefixes, 15/0 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 12.1.1.1 4 100 12 14 9 0 0 00:07:22 6 23.1.1.3 4 100 13 14 9 0 0 00:07:16 6 R3#show ip bgp all summary For address family: IPv4 Unicast BGP router identifier 3.3.3.3, local AS number 65002 BGP table version is 10, main routing table version 10 8 network entries using 936 bytes of memory 12 path entries using 624 bytes of memory 6/4 BGP path/bestpath attribute entries using 744 bytes of memory 3 BGP AS-PATH entries using 72 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 2376 total bytes of memory BGP activity 8/0 prefixes, 12/0 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 4.4.4.4 4 65002 10 12 10 0 0 00:06:36 2 13.1.1.1 4 65001 11 12 10 0 0 00:06:29 3 23.1.1.2 4 200 13 12 10 0 0 00:06:28 3 R4#show ip bgp all summary For address family: IPv4 Unicast BGP router identifier 4.4.4.4, local AS number 65002 BGP table version is 10, main routing table version 10 8 network entries using 936 bytes of memory 9 path entries using 468 bytes of memory 5/4 BGP path/bestpath attribute entries using 620 bytes of memory 2 BGP AS-PATH entries using 48 bytes of memory 0 BGP route-map cache entries using 0 bytes of memory 0 BGP filter-list cache entries using 0 bytes of memory BGP using 2072 total bytes of memory BGP activity 8/0 prefixes, 9/0 paths, scan interval 60 secs Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 3.3.3.3 4 65002 11 9 10 0 0 00:05:38 7