From: Ray Stevens (cisco-guy@rogers.com)
Date: Thu May 01 2003 - 16:19:44 GMT-3
If I understand your question correctly. You want to make sure that AS1500
and AS2000 do not see these routes as coming from AS20 and not to use it as
transit traffic.
Correct me on any of these points if I am wrong.
- When using the confederations the Sub-AS will be seen only within the
confederation.
- The External AS will only use you as a transit if you are advertising
routes from a different AS.
ie. if AS1500 advertises 10.0.0.0 and AS2000 advertises 20.0.0.0, if your
AS20 advertises these to the other AS then it will use you as a trasit AS.
Otherwise it will only send trafic to you that you advertise, in this case
the 4 routes from RTC.
- The AS-path filter only filters True AS, and not Confederate AS.
This is probably more of a question if I am correct on these points then an
answer.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
lg01
Sent: Tuesday, April 22, 2003 9:29 AM
To: ccielab@groupstudy.com
Subject: BGP AS
Hello group,
If I had...
RTA RTD
AS 1500 AS 2000
| |
| (normal EBGP) | (normal EBGP)
| |
********** **************
RTB *-----* RTC *
sub-as 8 * * sub-AS 200 *
********** **************
Now, both RTB & RTC are part of a big BGP confederation (confederation ID is
20)
Here comes the confusion:-
I have 4 BGP routes being injected by BGP network command by RTC. If I want
both RTA & RTB to be able to see these 4 routes, but I also want to ensure
that neither RTA nor RTD will use AS 20 for transit traffic, which means I
need to make sure that only those 4 routes within AS 20 should be
advertised. What AS-PATH access-list should I put on RTB?
I have tried...
- ip as-path access-list 2 permit ^$
- ip as-path access-list 2 permit ^200$
- ip as-path access-list 2 permit _200$
- ip as-path access-list 2 permit _8$
(of course, I put it on the neighbor out statment as well, but all of them
just
blocks all routes going out to RTA, any ideas?
Thanks.
H.
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