Uploaded byNetProtocol Xpert
BGP Update Source
This document discusses using a loopback interface as the update source for BGP sessions. It explains that when there are multiple paths between BGP neighbors, using a loopback interface ensures the BGP session will not go down if the physical interface fails. It provides the configuration to enable this by specifying the loopback interface in the neighbor update-source command. An example topology is shown connecting routers with EIGRP and configuring BGP between the routers using a loopback interface as the update source.
More Related Content
More from NetProtocol Xpert
BGP Update Source
- 1.
- 2. For BGP,a neighbor relationship to be established, source IP address of BGP packets sent by a router must be the same as neighbor ip-address set on the neighboring router. By default, packet’s source IP address is outgoing interface.
- 3. what if willneed to have two paths between BGP neighbors, which one to use to establish neighbor relationship? Please,Take a look at the topology.
- 4. In Perviousslide you see that there are two links between First router and Second router. We can establish two neighbor relationships, on both paths, but this is not a solution. So, we’ll establish only one neighborship with each other. BGP gives us an option to change the source of packets sent. In this case we can use Loopback interface as source of BGP packets sent between these neighbors. By using a loopback interface as source interface we have two paths between them, if one of paths fails, the other one will be used.
- 5. By using aloopback interface as update source, we also benefit from the fact that BGP session won’t go down when physical interface goes down. Update source can be configured per neighbor or per peer-group. To configure update source use the following command: neighbor {ip-addr | group-name} update-source interf where ip-addr | group-name is ip address of the neighbor or peer-group name, interf – is interface that will be used as update source. If you are interested in peer-group check BGP Peer Group lab.
- 6. Connection between all interfaces inthis topology, provided by using EIGRP: First(config)#router eigrp 1 First(config-router)# network 10.0.0.0 First(config-router)# network 192.168.0.0 First(config-router)# network 192.168.1.0 First(config-router)# no auto-summary Second(config)#router eigrp 1 Second(config-router)# network 10.0.0.0 Second(config-router)# network 192.168.0.0 Second(config-router)# network 192.168.1.0 Second(config-router)# no auto-summary
- 7. configuration related to BGP First First(config)#router bgp 65000 First(config-router)#neighbor 10.0.0.1 remote-as 65000 First(config-router)#neighbor 10.0.0.1 update-source loopback 0 Second Second(config)#router bgp 65000 Second(config-router)#neighbor 10.0.1.1 remote-as 65000 Second(config-router)#neighbor 10.0.1.1 update- source loopback 0
- 8. show ip bgp summary First#show ip bgp summary BGP router identifier 10.0.1.1, local AS number 65000 BGP table version is 1, main routing table version 1 Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd 10.0.0.1 4 65000 7 7 1 0 0 00:04:42 0 First#
- 9.