Lab 10-2: Confederation
Confederation takes a different approach to the full-mesh IBGP scalability problem (see Figure 10-7). A confederation AS is defined and the IBGP mesh divided into smaller sub-autonomous systems that connect via EBGP to the confederation AS. Some people refer to this as an "EIBGP" (External IBGP) session. Example 10-10 presents a confederation setup for the topology in Figure 10-7 featuring Zebra bgpd.
Example 10-10. BGP Confederation Example with Zebra
R3-bgpd# show running-config ... ! router bgp 3 bgp router-id 3.3.3.3 bgp cluster-id 3.3.3.3 bgp confederation identifier 3000 bgp confederation peers 1 2 neighbor 1.1.1.1 remote-as 1 neighbor 1.1.1.1 ebgp-multihop 3 neighbor 1.1.1.1 soft-reconfiguration inbound neighbor 1.1.1.1 update-source lo1 neighbor 2.2.2.2 remote-as 2 neighbor 2.2.2.2 ebgp-multihop 3 neighbor 2.2.2.2 soft-reconfiguration inbound neighbor 2.2.2.2 update-source lo1 neighbor INTERNAL peer-group neighbor INTERNAL remote-as 3 neighbor INTERNAL update-source lo1 neighbor INTERNAL route-reflector-client neighbor INTERNAL soft-reconfiguration inbound neighbor 3.3.3.1 peer-group INTERNAL neighbor 3.3.3.2 peer-group INTERNAL neighbor 3.3.3.4 peer-group INTERNAL ! ... R2-bgpd# show running-config ... ! router bgp 2 bgp router-id 2.2.2.2 bgp cluster-id 2.2.2.2 bgp confederation identifier 3000 bgp confederation peers 1 3 neighbor 1.1.1.1 remote-as 1 neighbor 1.1.1.1 ebgp-multihop 3 neighbor 1.1.1.1 soft-reconfiguration inbound neighbor 1.1.1.1 update-source lo1 neighbor 3.3.3.3 remote-as 3 neighbor 3.3.3.3 ebgp-multihop 3 neighbor 3.3.3.3 soft-reconfiguration inbound neighbor 3.3.3.3 update-source lo1 neighbor INTERNAL peer-group neighbor INTERNAL remote-as 2 neighbor INTERNAL update-source lo1 neighbor INTERNAL route-reflector-client neighbor INTERNAL soft-reconfiguration inbound neighbor 2.2.2.1 peer-group INTERNAL neighbor 2.2.2.3 peer-group INTERNAL neighbor 2.2.2.4 peer-group INTERNAL ! ... R1-bgpd# show running-config ... ! router bgp 1 bgp router-id 1.1.1.1 bgp cluster-id 1.1.1.1 bgp confederation identifier 3000 bgp confederation peers 2 3 neighbor 3.3.3.3 remote-as 3 neighbor 3.3.3.3 ebgp-multihop 3 neighbor 3.3.3.3 soft-reconfiguration inbound neighbor 3.3.3.3 update-source lo1 neighbor 2.2.2.2 remote-as 2 neighbor 2.2.2.2 ebgp-multihop 3 neighbor 2.2.2.2 soft-reconfiguration inbound neighbor 2.2.2.2 update-source lo1 neighbor INTERNAL peer-group neighbor INTERNAL remote-as 1 neighbor INTERNAL update-source lo1 neighbor INTERNAL route-reflector-client neighbor INTERNAL soft-reconfiguration inbound neighbor 1.1.1.2 peer-group INTERNAL neighbor 1.1.1.3 peer-group INTERNAL neighbor 1.1.1.4 peer-group INTERNAL ! ...
Figure 10-7. BGP Confederation
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