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ip-address— Neighbor’s IP address.
peer-group-name— Name of the peer group. See section 8-19.
Purpose: When a BGP router learns routes via EBGP, and those routes are advertised to an IBGP neighbor, the next-hop information is sent unchanged. This command allows a BGP router to change the next-hop information that is sent to IBGP peers. The next-hop information is set to the IP address of the interface used to communicate with the neighbor.
Cisco IOS Software Release: 10.0. Peer group support was added in Release 11.0.
Every prefix that is advertised using BGP contains next-hop information. Figure 8-15 shows the next-hop behavior for EBGP and IBGP. The advertisement for network 220.127.116.11/24 from Router B to Router A contains a next hop of 172.16.1.1. EBGP next-hop information is preserved when the prefix is advertised via IBGP. Router B advertises network 18.104.22.168/24 to Router C, with the next-hop information received from Router A.
On a multiaccess network, such as Ethernet or Token Ring, the next-hop behavior is as shown in Figure 8-16. Router B learns about network 22.214.171.124/24 from Router A via IGP. Router B advertises 126.96.36.199/24 to Router C via EBGP with the next-hop information set to the address of Router A. This is done to avoid the extra hop of sending packets destined to network 188.8.131.52/24 to Router B.
The next-hop behavior for a nonbroadcast multiaccess (NBMA) network is similar to that of a multiaccess network. Figure 8-17 shows a partially meshed NBMA network using a hub-and-spoke configuration. PVCs have been configured between the hub (Router B) and the spokes (Routers A and C). There is no PVC from Router A to C. Both PVCs are assigned to the same IP subnet, 172.16.1.0/24. Because the PVCs are on the same IP subnet, Router B sets the next-hop information for 184.108.40.206/24 to 172.16.1.1 when sending an update to Router C. Because Router C does not have a PVC to Router A, routing for this network will fail. In this situation, Router B needs to set the next hop for 220.127.116.11/24 to 172.16.1.2, as shown in the following configuration:
router bgp 1
neighbor 172.16.1.3 remote-as 2
neighbor 172.16.1.3 next-hop-self
Verify the next hop for network 18.104.22.168/24 on Router C by using the show ip bgp command on Router C:
rtrC#show ip bgp
BGP table version is 22, local router ID is 172.16.1.13
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 22.214.171.124/24 172.16.1.2 0 0 2 i
Verify that the BGP neighbors are in the Established state using the show ip bgp neighbors command.
If the neighbor relationship is not in the Established state, see section 8-23.
Verify the next-hop setting using show ip bgp.
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