Re: AS_PATH length and route selection (WAS: Strange BGP announcement)

["Sean M. Doran" <smd () clock org>]

Ben Black wrote:

| The key to this is that the administrative preference in question has domain
| scope.  Assuming you are correctly implementing iBGP, whether with a full
| mesh, reflectors, or confederations, and assuming consistent announcements
| from external route originators, then you can't make a loop because the
| same policy is in effect for all the routers in the AS.

You will not form a *persistent* loop or black-hole.   However,
as there is invariably some degree of propagation delay among iBGP
speakers, particularly in a large network, there can be short-lived
loops or black-holes when converging upon routing changes.

        Sean.