RE: AS-path prepending in confederations

From: Joe (groupstudy@comcast.net)
Date: Tue Dec 24 2002 - 00:19:06 GMT-3


Your problem is that you are prepending between the same AS, which
doesn't work. You only update the AS when you send to another AS, so
your prepend would have to take place on R2, not R4, assuming that R5 is
not in AS 65522.

Joe

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Ouellette, Tim
Sent: Monday, December 23, 2002 8:47 PM
To: 'ccielab@groupstudy.com'
Subject: FW: AS-path prepending in confederations

Rafael,

I can't remember at this time if AS-path prepending works in
confederations. If I make the assumption that it does, the route is
learned from a RR client and therefor when reflected to another client,
the update is not modified at all.

Does this sound like the issue your having?

Tim

-----Mensaje original-----
De: Lysyuk Andrew [mailto:lysyuk@ics.ua]
Enviado el: lunes 23 de diciembre de 2002 17:09
Para: ccielab@groupstudy.com
Asunto: AS-path prepending in confederations

Hello all!

I have faced with the problem of As-prepending in confederations. Are
there any restrictions on this issue? My topology is following:

    R2 --- R4
     |
    R5
   ...

I want to make 100.100.100.0/24 appeared on R2 as it traversed AS's 1000
and 1001. But it is not working. Can you help me where is my mistake?

Thanks in advance.
Andrew Lysyuk.

On R2:

interface Loopback0
 ip address 150.50.2.2 255.255.255.255

router bgp 65522
 no synchronization
 bgp log-neighbor-changes
 bgp confederation identifier 8888
 bgp confederation peers 65511 65533
 neighbor 150.50.17.1 remote-as 65511
 neighbor 150.50.100.4 remote-as 65522
 neighbor 150.50.100.4 route-reflector-client
 neighbor 150.50.100.5 remote-as 65522
 neighbor 150.50.100.5 route-reflector-client
 neighbor 150.50.100.6 remote-as 65522
 no auto-summary

On R4:
interface Loopback0
 ip address 150.50.4.4 255.255.255.255
!
interface Loopback1
 ip address 100.100.100.1 255.255.255.0
!
interface Loopback2
 ip address 100.100.101.1 255.255.255.0
!
router bgp 65522
 no synchronization
 bgp log-neighbor-changes
 bgp confederation identifier 8888
 bgp confederation peers 65511 65533
 network 100.100.100.0 mask 255.255.255.0
 network 100.100.101.0 mask 255.255.255.0
 neighbor 150.50.100.2 remote-as 65522
 neighbor 150.50.100.2 send-community
 neighbor 150.50.100.2 route-map R2 out
 no auto-summary
!
!
access-list 1 permit 100.100.100.0 0.0.0.255
access-list 2 permit 100.100.101.0 0.0.0.255
!
route-map R2 permit 10
 match ip address 1
 set as-path prepend 1000 1001
!
route-map R2 permit 20
 match ip address 2
 set community local-AS

But it is not working. Prefix 100.100.100.0/24 doesn't have

R2#show ip bgp
BGP table version is 15, local router ID is 150.50.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal Origin codes: i - IGP, e - EGP, ? - incomplete

   Network Next Hop Metric LocPrf Weight Path
*>i100.100.100.0/24 150.50.100.4 0 100 0 i
*>i100.100.101.0/24 150.50.100.4 0 100 0 i
*> 172.16.0.0/24 150.50.17.1 0 100 0 (65511) 500
i
*> 172.16.1.0/24 150.50.17.1 0 100 0 (65511) 500
i
*> 172.16.2.0/24 150.50.17.1 0 100 0 (65511) 500
i
*> 172.16.3.0/24 150.50.17.1 0 100 0 (65511) 500
i
*> 192.168.0.0 150.50.17.1 0 100 0 (65511) i
*> 192.168.0.0/22 150.50.17.1 100 0 (65511) i
*> 192.168.1.0 150.50.17.1 0 100 0 (65511) i
*> 192.168.2.0 150.50.17.1 0 100 0 (65511) i
R2#show ip bgp 100.100.100.0
BGP routing table entry for 100.100.100.0/24, version 15
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Flag: 0x208
  Advertised to non peer-group peers:
  150.50.17.1 150.50.100.5
  Local, (Received from a RR-client)
    150.50.100.4 (metric 64) from 150.50.100.4 (150.50.4.4)
      Origin IGP, metric 0, localpref 100, valid, confed-internal, best
R2# .
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.



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