Interaction of Non-BGP Routers with BGP Routers

Non-BGP routers inside the AS can reach the outside world by using the following two methods:

  • Injecting BGP into the IGP

  • Following default routes inside the AS

Injecting BGP into the IGP

Injecting full BGP routes into an IGP is not recommended; doing so will add excessive routing overhead to any IGP. Interior routing protocols were never meant to handle more than the networks inside your AS, perhaps in addition to a small number of exterior routes from other IGPs.

This does not mean that BGP routes should never be injected into IGPs. Depending on the number of BGP routes and how critical it is for them to be in the IGP, injecting partial BGP routes into IGP might be appropriate. If you ...

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