RE: How is BGP Preference List Actually Executed by BGP

From: OhioHondo (ohiohondo@columbus.rr.com)
Date: Fri Mar 14 2003 - 17:42:17 GMT-3


RE: How is BGP Preference List Actually Executed by BGP
Process?GlobalKnowledge would then be in conflict with what is published on
CCO. The original e-mail that I sent was cut and paste from CCO (under BGP
FAQ's).

----Original Message-----
From: Sanfilippo, Ted [mailto:Ted.Sanfilippo@PaeTec.com]
Sent: Friday, March 14, 2003 2:44 PM
To: 'OhioHondo'; ccielab@groupstudy.com
Subject: RE: How is BGP Preference List Actually Executed by BGP Process?

  In the Advanced BGP course from Global KNowledge they have a nice little
chart that shows how Filters are applied to BGP routing table:

  For all innound BGP routes to BGP Table:

  1. Distribute list in
  2. Filter-list in
  3. Default-weight
  4. Filter-list weight
  5. Route-map in

  For all outbound routes leaving BGP table to other BGP neighbors:

  1. Route-map out
  2. filter-list out
  3. Distribute list out

  For redistribution from BGP to IGP:

  1. Rotue-map on Redistribution line
  2. Distribute-list out

  From 1 - 5, 1 - 3, and 1 - 2 what it means is when the list is applied. So
for inbound BGP routes before they get put in the BGP routing table, if you
have a Distribute-list this will be applied first, and if you have a
route-map statment applied for inbound this will overwrite what you did to
the route via Distribute list command.

  -----Original Message-----
  From: OhioHondo [mailto:ohiohondo@columbus.rr.com]
  Sent: Friday, March 14, 2003 10:05 AM
  To: ccielab@groupstudy.com
  Subject: How is BGP Preference List Actually Executed by BGP Process?

  Everyone

  I found the following preference list on CCO.

  For inbound updates the order of preference is:
  route-map
  filter-list
  prefix-list or distribute-list

  My question is, how does the BGP process handle this. Is the following
true?

  If an inbound route-map exists then inbound filter-lists, prefix-lists and
  distribute-lists are not even considered.



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