Thursday, April 25, 2019

MPLS over DSL on Cisco C1117

I was recently tasked to upgrade 14 CPE routers from old C800 series to C1117s as the older devices could no longer keep up with circuit bandwidth upgrades.

Me being naive thought it was going well after the first 5 circuits, till I came across upgrading the first of the FTTC circuit that is.

The setup we have for this particular client is using multi vrf on the CPE with MPLS integrated into our core using iBGP as a routing protocol.

The first thing I noticed after the upgrade was that the router was not learning BGP routes. After lots of staring, swearing and playing around, my colleague realised that the only way to bring up BGP and LDP on the CPE was to remove the static /32 to the MPLS first hop.

Once removed routes and labels were learnt as normal. However, without the route, MPLS cannot be forwarded to the first hop.

This brings me to a chicken and egg scenario I just cannot get my head around.

The only difference we can actually see is a dialler layer 2 MTU reduction of 8 bytes between the models that can not me increased.

The router config is almost a direct port from the C880 to the C1117 and has worked perfectly for all the EAD circuits.

Does anyone have any ideas what may be happening here that would affect the newer routers? Are we just blind missing something?

This has effectively brought all our upgrade projects to a halt as the new devices are not fit for purpose till we can fix whatever is happening here.

I know I have probably not explained this very well but I am more than happy to answer questions.

Thanks all!



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