Thursday, 30 September 2010

MPLS Troubleshooting

I'm nearly at the end of INE's MPLS CoD, and the last few lessons are about advanced configurations for Internet Service VPNs etc. Following Keith's advice about making sure I understood the basics before continuing, I started my MPLS lab again from scratch, and came across an interesting problem..

Now, i'm assuming you know the topology for this (if not, it's over here).

I'd configured everything as per the videos, with the 192.168.3.x/32 network as loopback0 for each of the Provider devices, and MP-BGP running between the PE's to exchange VRF routing information.

I ran into a problem with VRF Cust_A, between the sites A1-Central and A2-Remote, and it was a very good test of my Troubleshooting skills...

Both PE-2 and PE-3 had learned the correct routes in their VRF routing tables, but traffic was not passing successfully;

PE-2#show ip route vrf Cust_A <- all as expected
PE-2#ping vrf Cust_A 203.1.0.1 <- timeout

PE-3 could ping the loopback0 of PE-2 (using it's own loopback0 as, but PE-2 could not ping the loopback of PE-3;

PE-2#ping 192.168.3.3 so lo 0 <- timeout
PE-3#ping 192.168.3.2 so lo 0 <- successful

PE-2 was learning the route correctly for PE-3's loopback0;

PE-2#show ip route 192.168.3.3 <- as expected, via interface to router P

The CEF table on PE-2 did not look as expected;

PE-2#show ip cef 192.168.3.3 255.255.255.255 <- not as would be expected!


I'll leave things there for now, and try and upload the screenshots..

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