From: Scott Morris (smorris@ipexpert.com)
Date: Sun Jul 29 2007 - 22:36:56 ART
Heheheh.. In the event of your multihoming, I think your upstream may be a
little upset to know that you are impersonating them and only advertising a
small set of routes (e.g. not wanting to be a transit path!).
So very often we'll have private AS's to use for purposes like this where
you want to run BGP, but are not multihoming, or simply that you don't have
provider independent space and even if you are multihoming you aren't really
advertising anything.
If you DO have something to advertise, then you need an AS number. I
believe they're only on 49000 something for assignments, so there's still
room to grow.
At the same time, they're just wrapping up the 4-byte AS number extensions,
so no fear of running out now!
But with the interconnected world of BGP, if you truly have a need to run
BGP, then you most likely will need your own AS number to do so. Otherwise,
work with your ISP for private AS assignment, but don't impersonate them,
they will likely not find the humor in it!
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
smorris@ipexpert.com
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Gregory Gombas
Sent: Sunday, July 29, 2007 2:05 PM
To: Group study
Subject: Unique AS number when connecting to two different ISP's?
When connecting to the internet via two different ISP's, why is it necessary
to have a unique AS?
What if you simply configured your BGP router with the same AS number as one
of your ISP's?
Considering there are only 64511 unique AS numbers, I assume that most if
not all the AS numbers are already taken. What do companies do in the case
they cannot get their own AS number and need to multihome?
Thanks,
Greg
This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:42 ART