Command:

bgp confederation identifier


Mode:

Router(config-router)#


Syntax:

bgp confederation identifier as-number
no bgp confederation identifier as-number

 

Syntax Description:

as-number

Autonomous system number that internally includes multiple autonomous systems.

 

Command Description:

To specify a BGP confederation identifier, use the bgp confederation identifier command in router configuration mode. To remove the confederation identifier, use the no form of this command.

One way to reduce the internal BGP (iBGP) mesh is to divide an autonomous system into multiple autonomous systems and group them into a single confederation. Each autonomous system is fully meshed within itself and has a few connections to another autonomous system in the same confederation. Even though the peers in different autonomous systems have external BGP (eBGP) sessions, they exchange routing information as if they are iBGP peers. Specifically, the next hop, Multi Exit Discriminator (MED), and local preference information is preserved. The preservation of this information enables to you to retain a single Interior Gateway Protocol (IGP) for all the autonomous systems. To the outside world, the confederation looks like a single autonomous system.


Example:

In the following example, the autonomous system is divided into autonomous systems 4001, 4002, 4003, 4004, 4005, 4006, and 4007 and identified by the confederation identifier 5. Neighbor 10.2.3.4 is someone inside your routing domain confederation. Neighbor 10.4.5.6 is someone outside your routing domain confederation. To the outside world, there appears to be a single autonomous system with the number 5:

Router(config)#router bgp 4001
Router(config-router)#bgp confederation identifier 5
Router(config-router)#bgp confederation peers 4002 4003 4004 4005 4006 4007
Router(config-router)#neighbor 10.2.3.4 remote-as 4002
Router(config-router)#neighbor 10.4.5.6 remote-as 510


Misconceptions:

None


Related Commands:

bgp confederation peers

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