From: Kelly, Russell G (Russell_Kelly@eu1.bp.com)
Date: Thu Nov 20 2003 - 13:10:09 GMT-3
Sorry should read:
AS1 and AS2 have all routers running BGP but AS3 redistributes BGP
learnt from AS1 and AS2 into
OSPF (and needs to redistributes only it's own OSPF routes into BGP)
-----Original Message-----
From: Kelly, Russell G
Sent: 20 November 2003 15:58
To: ccielab@groupstudy.com
Subject: BGP Regular Expressions for as-path filtering
I have 3 AS's chained together as below:
| AS 1 | -> | AS2 | -> | AS3 |
AS1 and AS2 have all routers running BGP but AS redistributes BGP into
OSPF (and redistributes it's own OSPF routes into BGP). I want AS3 to
only redistribute routes originating in AS1 and AS2 into OSPF (and not
redistribute these back into BGP!!!!!) and I am trying to come up with a
regular expression to achieve this. I am not too sure on the as-path 1
^2 1$ regular expression, or the redistribution tagging for AS1. Will
the 'better' reg expression be:
ip as-path access-list 1 permit ^2.* (i.e. anything coming through
AS2???)
The route maps and as-path statements currently are:
ip as-path access-list 1 permit ^2 1$
ip as-path access-list 2 permit ^2$
route-map BGP2OSPF permit 10
description Allow AS1 Routes
match as-path 1
set metric 100
set metric-type type-1
set tag 2 1
!
route-map BGP2OSPF permit 20
description Allow AS2 Routes
match as-path 2
set metric 100
set metric-type type-1
set tag 2
!
route-map OSPF-TO-BGP deny 10
match tag 2
!
route-map OSPF-TO-BGP deny 20
match tag 2 1
!
route-map OSPF-TO-BGP permit 30
Russ
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