NOCWiki

IOS XR

BGP Local-AS

Let’s assume a member would like to use BGP as number 65111 which is already in use by a different member. In this case Deutsche Boerse will assign a free AS number to that member (in our example 65200) If the member is not willing to use the free AS number he has to use bgp local-as, no-prepend and replace-as.

BGP “local-as” only

The configuration will look like this:

TF-RMIL0115 (AP POP router)

router bgp 12625

!

address-family ipv4 vrf M_65200

neighbor 10.20.100.38 remote-as 65200

neighbor 10.20.100.38 activate

neighbor 10.20.100.38 prefix-list trading_networks_A out

neighbor 10.20.100.38 route-map trading_member_in in

neighbor 10.20.100.38 maximum-prefix 20

!

R004446 (member router)

router bgp 65111

address-family ipv4 vrf M_65111

neighbor 10.20.100.37 remote-as 12625

neighbor 10.20.100.37 local-as 65200

The “Local-as” and “real” as numbers are visible within the AS PATH. The BGP tables will look like this:

TF-R004446#sh ip bgp vpnv4 vrf M_65111

TF-RMIL0115#sh ip bgp vpnv4 vrf M_65200

BGP “local-as” + “no-prepend”

The configuration on the POP router will not change. The configuration on the member router will look like this:

TF-R004446#

router bgp 65111

address-family ipv4 vrf M_65111

neighbor 10.20.100.37 remote-as 12625

neighbor 10.20.100.37 local-as 65200 no-prepend

The local as number on member end will disappear from the AS PATH. The BGP table will look like this:

TF-R004446#sh ip bgp vpnv4 vrf M_65111

TF-RMIL0115#sh ip bgp vpnv4 vrf M_65200

BGP “local-as” + “no-prepend” + “replace-as”

The configuration on the POP router will not change. The configuration on the member router will look like this:

TF-R004446#

router bgp 65111

address-family ipv4 vrf M_65111

neighbor 10.20.100.37 remote-as 12625

neighbor 10.20.100.37 local-as 65200 no-prepend replace-as

The members “real” as number on the POP router will disappear. The BGP tables will look like this:

TF-R004446#sh ip bgp vpnv4 vrf M_65111

TF-RMIL0115#sh ip bgp vpnv4 vrf M_65200