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Re: bgp route-map
From: Matt Levine <matt () deliver3 com>
Date: Mon, 25 Aug 2003 15:30:01 -0400

On Monday, August 25, 2003, at 3:00 PM, Haesu wrote:

Yes, I've tried that too.. But what I am thinking of doing is, using a route-map/bgp-announcement based version of building 'prefix-list' or 'distribute-list' to decide whether to accept route or not..

But as you said, I don't think that is possible heh..

Except that what you are proposing would allow your customer to announce 2 /16's just fine from within one of rob's bogon /8's, as the 2 /16's wouldn't be in your rib.


  Haesu C.
  TowardEX Technologies, Inc.
  WWW: http://www.towardex.com
  E-mail: haesu () towardex com
  Cell: (978) 394-2867

On Mon, Aug 25, 2003 at 02:57:57PM -0400, ww () styx org wrote:
I don't think what you are suggesting is directly possible, although I can think of something that accomplishes the same thing, and only requires extra configuration on
the peering session with the route server.

For prefixes recieved from the bogon route server, apply a route map that will (1) send traffic to a Null0 bit sink and (2) set the local preference for these routes to a value suitably large so that the same prefixes learned from other peers never get


On Mon, 25 Aug 2003 14:39:59 -0400, Haesu wrote
Hi all,

Wondering if anyone would know whether such feature in IOS exists or

Most of the time, people use route-maps on bgp neighbors or peer-
groups to set an attribute,etc on a prefix that is being announced
OUTbound or INbound.

However: On prefixes being announced to me INBOUND, is there a
feature  to set in route-map so that it checks whether the
advertised prefix is already existing in local RIB?

Like for example, I am one of the users who receive bogon
advertisements from Rob's route-server.

Now, when I receive prefixes either from my upstream AS or my
customers doing bgp with me, I can setup a route-map on the neighbor
so that it compares the prefix being announced by neighborAS with
existing Rob's bogon prefix in the RIB with bogon route-server
community 65333:888.

If the prefix being announced gets a match with existing prefix with
65333:888 already in the router, the route-map would cause a DENY.
Thus, making Rob's bogon announcement from his route-server, a bogon
route filtering list for me to use on my customers/peers..

If you are not understanding what I am saying, feel free to yell at
me to clear up..

This would make it much easier to create dynamic bgp-based route
filtering list in my opinion... I am not here to discuss the
feasibility of whether doing or inventing this dynamic method of
filtering bgp routes; I am rather asking this question to see if
anyone is doing something similar to this as it may be useful.



-- Sincerely,
  Haesu C.
  TowardEX Technologies, Inc.
  WWW: http://www.towardex.com
  E-mail: haesu () towardex com
  Cell: (978) 394-2867

Matt Levine <matt () deliver3 com>
"The Trouble with doing anything right the first time is that nobody appreciates how difficult it was." -BIX

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