Vyatta NOS documentation

Learn how to install, configure, and operate Vyatta Network Operating System (Vyatta NOS), which helps to drive our virtual networking and physical platforms portfolio.

Confederations

Confederations enable you to reduce the size and complexity of the iBGP mesh. In a BGP confederation, a single AS is divided into multiple internal sub-AS to help keep the number of iBGP peer connections manageable. Each sub-AS is assigned its own AS number; this is typically assigned from the private AS number space, which ranges from 64512 through 65534. Within a sub-AS, all the standard iBGP rules, including full-mesh peering, apply. The connections between confederation sub-AS use eBGP peering. One or more eBGP connections can be made between each sub-AS. The sub-AS are grouped as a confederation, which advertises as a single AS to external peers.

The following figure shows the large number of iBGP connections that must be configured in even a moderately sized AS. In this example, 14 routers are participating in iBGP.

Figure 1. iBGP full mesh

The following figure shows a BGP confederation that splits the single AS shown in the preceding figure into three sub-AS, which each use private AS numbers. Within each sub-AS, all of the iBGP peers are fully meshed. The sub-AS are connected to one another using an eBGP connection.

Figure 2. BGP confederation