BGP update source loopback0 commands - GPON Solution

BGP update source loopback0 commands

BGP update source loopback0:

Today i will discuss why we use BGP update source loopback0 for establishing  neighbor relationship between bgp peering. If we have two paths between BGP neighbors, then which path use to establish neighbor relationship? don’t worry i will describe you briefly, please look bellow diagram:

BGP update source loopback0

BGP update source loopback0

In this topology we see that there are two links between router R1 and router R2. We can establish two neighbor relationships, on both paths, but this is not a good solution. So, we’ll establish only one neighbor ship 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.

By using a loopback 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.

For IGP connection of two router we use OSPF protocol in this topology, so let’s go our configuration part.

BGP update source loopback0 Configuration Example:
Basic Configure R1:
R1#conf t
R1(config)#int fa0/1
R1(config-if)#ip address
R1(config-if)#no shutdownR1(config-if)#int fa0/0
R1(config-if)#ip address
R1(config-if)#no shutdown
R1(config-if)#exitR1(config)#interface loopback 0
R1(config-if)#ip address

OSPF Configure R1:
R1(config)#router ospf 1
R1(config-router)#network area 0
R1(config-router)#network area 0
R1(config-router)#network area 0
BGP Configure R1:
R1(config)#router bgp 100
R1(config-router)#neighbor remote-as 100
R1(config-router)#neighbor update-source loopback 0
Basic Configure R2:
R2#conf t
R2(config)#int fa0/1
R2(config-if)#ip address
R2(config-if)#no shutdownR2(config-if)#int fa0/0
R2(config-if)#ip address
R2(config-if)#no shutdown
R2(config-if)#exitR2(config)#int loopback 0
R2(config-if)#ip address

OSPF Configure R2:
R2(config)#router ospf 1
R2(config-router)#network area 0
R2(config-router)#network area 0
R2(config-router)#network area 0
BGP Configure R2:
R2(config)#router bgp 100
R2(config-router)#neighbor remote-as 100
R2(config-router)#neighbor update-source loopback 0
Here pink color highlighted commands are changed BGP update-source. Now we verify our configuration.
BGP update source loopback0 command

BGP update source loopback0 command

From Router R1 bgp summary table we see neighbor is R2 router’s loopback 0 IP. so it’s work.



Hi! I am Shahed. Currently working as a Network Engineer. I want to build up my carrier in Networking field.

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BGP update source loopback0 commands was last modified: February 11th, 2015 by Shahed



One Response to BGP update source loopback0 commands

  1. Roberto says:

    Hi, thank you very much for this post! My doubt was answer completely. I hope you keep doing more posts like this one.

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