[21717] in North American Network Operators' Group
Re: AS_PATH length and route selection (WAS: Strange BGP announcement)
daemon@ATHENA.MIT.EDU (Sean M. Doran)
Wed Nov 18 17:59:17 1998
From: "Sean M. Doran" <smd@clock.org>
To: black@layer8.net, nanog@merit.edu
Date: Wed, 18 Nov 1998 14:30:59 -0800
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.
