Scalability with Border Gateway Protocol (BGP4)
BGP is a complex routing protocol that requires that all routers be fully meshed in an Internal BGP (IBGP) network. To maintain accurate and up-to-date information in IBGP networks, all routers must peer to one another.
Consider a network consisting of 100 routers. Having this many routers leads to a large number of TCP BGP peers. In fact, you can easily calculate the number of peers by using the formula n(n-1)/2, where n is the number of BGP routers.
Note
To avoid routing loops, BGP only propagates updates learned from IBGP connections to other IBGP sessions that are fully meshed. Fully meshed networks contain a BGP peer to every BGP speaker in the network.
For a 100-router network, there are ...
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