From: Bill Dicks (wdicks@xxxxxxxxxxxxxxxxxx)
Date: Thu Jul 20 2000 - 12:25:37 GMT-3
The attribute-map is used to change the attributes of the aggregate route.
Remember that an aggregate route has the combined attributes of its more
specific routes. For example, if 191.180.10.0/24 has its community set to
no-export, then the aggregate 191.180.0.0/16 will have community set to
no-export and the aggregate will not be passed very far. You would use the
attribute-map to set the community to none so the route would be propagated
throughout the Internet (see Internet Routing Architectures by Halabi, pp.
360-362).
The advertise-map is used to only select certain more specific routes to
base the aggregate on. If the aggregate is using the as-set attribute for
loop prevention (as-set is like AS-path, only order does not matter), then
your AS may not be able to send the aggregate to AS's with more specific
routes because their AS is part of the AS-SET. For example, if you are AS
1, and AS2 is sending you 100.1.1.0/24 and AS3 is sending you 100.1.2.0/24,
then the as-set for the aggregate 100.1.0.0/16 would be {2 3}. When AS 2
and 3 receive a route with an as-set that includes their own AS, they will
not accept that route because they think it already passed through their own
AS. You would use the advertise-map to choose to base the aggregate only on
100.1.1.0/24. This would have the as-set then only be {2} and AS3 would
then accept the 100.1.0.0/16 route because its own AS is NOT in the as-set.
This scenario was on pp 363-365 of the same book above. If you want to know
BGP, you should get this book.
Bill
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jansen
Sent: Thursday, July 20, 2000 5:30 AM
To: ccielab
Subject:
Hi,
Can anybody tell me what's the difference between these two commands:
aggregate-address advertise-map & aggregate-address attribute-map
i have read the description on cisco CD,but ....
Can anybody give me a example about how to use them?
Thanks a lot.
Best Regards.
Jansen
jysh@teamsun.com.cn
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