In this article, i will not go deeply into the issue of configuring MPLS-VPN. The steps were mentioned very clearly in an earlier post. MPLS-VPN Tutorial has all the required details. I would like to mention a mis-step that i did while doing another MPLS-VPN configuration. what resulted in routing updates to work properly. But no traffic was going from one end to another end. After countless of hours, i found the mistake. Before proceeding, the image below shows the sample network. Download the configurations. They can be used to simulate the network using GNS3.
While i was configuring the BGP VPN section i got the following error.
R6(config-router)# neighbor 188.8.131.52 remote-as 100
R6(config-router)# neighbor 184.108.40.206 update-source Loopback0
R6(config-router)# address-family vpnv4
R6(config-router-af)# neighbor 220.127.116.11 activate
R6(config-router-af)# neighbor 18.104.22.168 send-community extended
*Mar 1 02:08:59.455: %BGP-5-ADJCHANGE: neighbor 22.214.171.124 Up
*Mar 1 02:08:59.463: %BGP-4-VPNV4NH_MASK: Nexthop 126.96.36.199 may not be reachable from neigbor 188.8.131.52 – not /32 mask
Then, i did not mind the error (highlighted in bold) and carried on with configurations. At the end, i had a full working network with proper routing updates in the MPLS-VPN plan. But no traffic is going. I had to troubleshoot many things. Till the end, i decided to re-configure the routers all over. Then i noticed the error. decided to fix it. Changed the loopback address from /24 to /32. The moment i did that, the traffic started passing.
What i learned, is that “Don’t ignore any messages the IOS gives you while configuring”