Inter AS---- Model B

In this case specific instances of VPRN is not required to be created on the ASBR

In this case mp-ebgp is used to transport vpn-ipv4 routes between the autonomous system

The PE and the ASBR are connected to each other using MP-IBGP the PE and the ASBR's are connected directly or are connected with the help if RR

The primary difference between MP-ibgp and mp-ebgp is the next hop attribute is changed when there is an ebgp session then when there is an mp-ibgp session

The LSP path terminates on the ASBR originating the update.

The ASBR has to assign a new label for the route before sending it via the mp-ebgp peer ie to its peer ASBR

See the figure for the detailed description of the routes being generated from one CE to another CE

Configuration for Model B:-

1> CE-PE routing:-

2> VPRN configuration on the PE:-

Configuration of MP-ibgp between the PE and the ASBR:-



For MP-EBGP between the two AS's use the command enable-inter-as-vpn

Verification:-

CE-PE routing verification:-

show router bgp summary

PE-ASBR routing verification

Show router bgp summary

ASBR-ASBR routing verification:-

show router bgp summary

CE routing table:-

show router route-table

PE route table verification:-

show router 10 route-table

As seen below when the route is advertised from ASBR2 to PE2 the next hop is modified as the next hop is modified the vpn label is modified as well. This is also true in the case when the labels are advertised between the ASBR's as well.

BGP inter AS label can be viewed by using the following command:-