bgp soo and route-maps

Hello,

I need a clarification about bgp soo. In the example below R4 and R5
are connected with two links 10.1.45.0/24 and 10.1.100.0/24:

R4 (PE)===========R5 (CE)
AS65001 AS6015

R5 (CE) advertises network 5.0.0.0.
The problem is that R5 (CE) receives it's own route redistributed back from R4:
R5#
R5#sh ip bgp | b Network
   Network Next Hop Metric LocPrf Weight Path
* 5.0.0.0 10.1.100.4 0 65001 65001 i
*> 0.0.0.0 0 32768 i
R5#

To remediate, SOO is configured on R4:

1. Route-map is configured:

route-map SOO-IN permit 10
 set extcommunity soo 1:100

2. Route map is applied:

router bgp 65001
!
 address-family ipv4 vrf CB
  neighbor 10.1.45.5 route-map SOO-IN in
  neighbor 10.1.100.5 route-map SOO-IN in

AT THIS POINT the problem is solved. R5 does not contain it's own
route back from R4:

R5#sh ip bgp | b Network
   Network Next Hop Metric LocPrf Weight Path
*> 5.0.0.0 0.0.0.0 0 32768 i

HOWEVER the workbook goes extra few steps and confiures additional
filtering on PE OUT to CE:

ip extcommunity-list 1 permit soo 1:105
route-map SOO-OUT deny 10
 match extcommunity 1
route-map SOO-OUT permit 99
!
router bgp 65001
!
 address-family ipv4 vrf CB
  neighbor 10.1.45.5 route-map SOO-OUT out
  neighbor 10.1.100.5 route-map SOO-OUT out

My question is why second route-map OUT is configured on PE. It looks
like only marking on PE incoming routes with ext community soo works
OK.

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Received on Fri Sep 10 2010 - 12:54:44 ART