Nov 21 2008
Inter AS MPLS VPN Option C – Packet Capture
I setup the following topology.
I configured a loopback address with ip address 10.10.10.10 on PE1 and put it inside the VRF for VPN A. One PE1 I could see the VPN label being generated by BGP as below.
sh ip bgp vpnv4 all labels
Network Next Hop In label/Out label
Route Distinguisher: 65300:1 (CUST)
10.10.10.10/32 0.0.0.0 19/nolabel
As you can see the “In label” is 19. To confirm the label is not changed anywhere in the path I also checked the label for 10.10.10.10 on ASBR2 and PE2, see below for output.
ASBR2
ASBR2#sh ip bgp vpnv4 all labels
Network Next Hop In label/Out label
Route Distinguisher: 65300:1
10.10.10.10/32 1.1.1.1 nolabel/19
PE2
PE2#sh ip cef vrf CUST 10.10.10.10
10.10.10.10/32
nexthop 11.0.0.5 FastEthernet1/0 label 19 19
PE2#sh ip bgp vpnv4 all labels
Network Next Hop In label/Out label
Route Distinguisher: 65300:1
10.10.10.10/32 1.1.1.1 nolabel/19
I also ran a packet capture on the ASBR2 interface which peers with ASBR1 and sure enough when I ran a ping to 10.10.10.10 I saw a dual stacked MPLS frame, with a VPN label of 19.
