BGP SoO

Hello Everyone,

I am having difficulty understanding one of the Narbik's BGP SoO lab. Here
is the lab setup removing unnecessary components :

R4 acting as a PE is dual homed to R5 CE via FR p-2-p and serial link. R5
(CE) is advertising it's loopback 5.5.5.5 to R4 via link and it learned same
route back from R4. The BGP table on R5 looks like this:

R5#show ip bgp

BGP table version is 37, local router ID is 5.5.5.5

Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

* 1.0.0.0 10.1.100.4 0 65001 65015 i

*> 10.1.45.4 0 65001 65001 i

* 5.0.0.0 10.1.100.4 0 65001 65015 i

*> 0.0.0.0 0 32768 i

* 192.168.1.0 10.1.100.4 0 65001 65015 i

*> 10.1.45.4 0 65001 65001 i

* 192.168.5.0 10.1.100.4 0 65001 65015 i

*> 0.0.0.0 0 32768 i

Once I implement the BGP SoO via route-map or neighbour command, the BGP
table on R5 stop learning it's loopback 5.5.5.5 from frame connection.

R5#show ip bgp

BGP table version is 43, local router ID is 5.5.5.5

Status codes: s suppressed, d damped, h history, * valid, > best, i -
internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

* 1.0.0.0 10.1.100.4 0 65001 65015 i

*> 10.1.45.4 0 65001 65001 i

*> 5.0.0.0 0.0.0.0 0 32768 i

* 192.168.1.0 10.1.100.4 0 65001 65015 i

*> 10.1.45.4 0 65001 65001 i

*> 192.168.5.0 0.0.0.0 0 32768 i

It's all as per plan:

R4 Configuration before BGP SoO

router bgp 65001

no bgp default ipv4-unicast

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 65001

neighbor 3.3.3.3 update-source Loopback0

!

address-family vpnv4

neighbor 3.3.3.3 activate

neighbor 3.3.3.3 send-community extended

exit-address-family

!

address-family ipv4 vrf CB

neighbor 10.1.45.5 remote-as 65015

neighbor 10.1.45.5 activate

neighbor 10.1.45.5 as-override

neighbor 10.1.100.5 remote-as 65015

neighbor 10.1.100.5 activate

no synchronization

exit-address-family

R4 Configuration after BGP SoO

router bgp 65001

no bgp default ipv4-unicast

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 65001

neighbor 3.3.3.3 update-source Loopback0

!

address-family vpnv4

neighbor 3.3.3.3 activate

neighbor 3.3.3.3 send-community extended

exit-address-family

!

address-family ipv4 vrf CB

neighbor 10.1.45.5 remote-as 65015

neighbor 10.1.45.5 activate

neighbor 10.1.45.5 as-override

neighbor 10.1.45.5 soo 65015:1

neighbor 10.1.100.5 remote-as 65015

neighbor 10.1.100.5 activate

neighbor 10.1.100.5 soo 65015:1

no synchronization

exit-address-family

Now back to Narbik's configuration after BGP SoO on R4, the results are same
if I do below configuration

route-map TST permit 10

set extcommunity soo 1:105

ip extcommunity-list 1 permit soo 1:105

route-map TEST deny 10

match extcommunity 1

route-map TEST permit 90

router bgp 65001

no bgp default ipv4-unicast

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 65001

neighbor 3.3.3.3 update-source Loopback0

!

address-family vpnv4

neighbor 3.3.3.3 activate

neighbor 3.3.3.3 send-community extended

exit-address-family

!

address-family ipv4 vrf CB

neighbor 10.1.45.5 remote-as 65015

neighbor 10.1.45.5 activate

neighbor 10.1.45.5 as-override

neighbor 10.1.45.5 route-map TST in

neighbor 10.1.45.5 route-map TEST out

neighbor 10.1.100.5 remote-as 65015

neighbor 10.1.100.5 activate

neighbor 10.1.100.5 route-map TST in

neighbor 10.1.100.5 route-map TEST out

no synchronization

exit-address-family

R5 Configuration:

router bgp 65015
 no synchronization
 bgp log-neighbor-changes
 network 5.0.0.0
 network 192.168.5.0
 neighbor 10.1.45.4 remote-as 65001
 neighbor 10.1.100.4 remote-as 65001
 neighbor 10.1.100.4 allowas-in
 no auto-summary

I'm confused as why I am getting same results in terms on R5 doesn't learn
it's loopback 5.5.5.5 when we implement configuration in two different ways.
The first configuration is simple and do the same task and Narbik
configuration provide same results.

I am sure, if I am missing something. Can anyone please shed some light on
my ignorance. I apologise if the post is confusing and long, but will be
highly appreciated, is some please help.

Thanks,

Bilal Hansrod

Blogs and organic groups at http://www.ccie.net
Received on Thu Jun 09 2011 - 22:10:58 ART