What is a BGP Confederation?


By its true definition, a confederation is an organization which consists of a number of parties or groups united in an alliance or league.

But what is a BGP confederation?

BGP Confederation

A BGP confederation is an alternative method to route reflectors, used to reduce the number of BGP peerings within a single AS. Furthermore it is a single AS that has been subdivided into a number of internal sub-AS’s, yet still, advertise as a single AS to external peers [1] .



Figure 1 – BGP Confederation.


Within the confederation, each sub-AS (inter-confederation) is assigned a private AS number (64512-65535). Though eBGP is used to peer each of the sub-AS’s, the rules of iBGP still apply to each inter-confederation i.e attributes are not altered and an iBGP full-mesh is still required.

Routing Loops

To avoid routing loops, a sub-AS uses a confederation sequence, which operates like an AS path but uses only the privately assigned sub-AS numbers. [2] These are stripped prior to the router sending UPDATEs via eBGP.


[1] “BGP confederation – Wikipedia.” https://en.wikipedia.org/wiki/BGP_confederation . Accessed 18 Nov. 2017.
[2] “Understanding BGP Confederations – Technical … – Juniper Networks.” https://www.juniper.net/documentation/en_US/junos/topics/concept/routing-protocol-bgp-security-confederation-understanding.html . Accessed 18 Nov. 2017.

Rick Donato

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