RE: BGP & community

From: Scott Livingston (scottl@sprinthosting.net)
Date: Wed Feb 19 2003 - 01:15:11 GMT-3


Actually, your 1st config should have referenced an AS filter such as
this:
!
ip as-path access-list 11 permit ^$ <----- Means = originated on this
!router.
!

The 2nd config you can see that there is an implicit 'no-export' on all
prefix's.

Hope I am right and I hope that helps.

-scott

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
pita40
Sent: Tuesday, February 18, 2003 6:30 PM
To: ccielab@groupstudy.com
Subject: BGP & community

I have a question from one of the commecial labs.

Configure BGP such that BGP routes learned by AS 111 from AS 4799 are
not
passed onto their EBGP peers

I used the first config with as-path. When I go to the bgp peer (BB1) to
look
at the attribute for the routes it learned from R1 I get a shock that it
is
not advertising to any peer.
When I remove as-path statement I get not advertised to EBGP peer which
is the
correct answer.
Please help clarify why the routes are behaving like this.

R1

router bgp 65013
 bgp confederation identifier 4799
 bgp confederation peers 65053
 neighbor 150.50.33.33 remote-as 65013
 neighbor 150.50.33.33 update-source Loopback0
 neighbor 150.50.111.111 remote-as 111
 neighbor 150.50.111.111 send-community
 neighbor 150.50.111.111 route-map comm out
 no auto-summary

ip as-path access-list 11 permit _4799_

route-map comm permit 10
 match as-path 11
 set community no-export
!
route-map comm permit 20

With the above config I get the following on BB1 with is nei
150.50.111.111

bb1#sh ip bgp 133.133.133.0 255.255.255.0
BGP routing table entry for 133.133.133.0/24, version 47
Paths: (1 available, best #1)
  Not advertised to any peer
  4799
    150.50.111.1 from 150.50.111.1 (200.200.11.11)
      Origin incomplete, localpref 100, valid, external, best, ref 2

When I remove the as-path command like this

 route-map comm permit 10
  set community no-export

I get this on BB1

bb1#sh ip bgp 133.133.133.0 255.255.255.0
BGP routing table entry for 133.133.133.0/24, version 76
Paths: (1 available, best #1, not advertised to EBGP peer)
  Not advertised to any peer
  4799
    150.50.111.1 from 150.50.111.1 (200.200.11.11)
      Origin incomplete, localpref 100, valid, external, best, ref 2
      Community: no-export



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