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Reprovisioning of customer's VRF for CSC connections


I experienced a problem where I had to reprovision a customer's VRF in a PE via the ISC everytime the customer's CE hanged or the BGP flapped (CSC connection). The routing table looked good and I could ping from my PE to their CE (PE to them) and even from their CE to CE. We couldn't figure out the problem. After reprovisioning, CSC worked fine and traffic flows as usual.


Re: Reprovisioning of customer's VRF for CSC connections

Well Nariman,

You are using BGP for the label exchange I believe. or is it LDP.

Can u also check when there is a flap what is the status of the MPLS forwarding table.

So you see any changes there, as well as compare with MPLS forwarding table on the customer side PE before flap and after flap.

Best way is to get these details by simulating the same in the lab, if possible or get it live when happens. If you already have these details please upload.



New Member

Re: Reprovisioning of customer's VRF for CSC connections


We're using LDP for PE to CE.

Customer's BGP flapped due to the mtu size on our MPLS backbone. The issue was settled when we rediverted to a different link (limitation was actually in our SDH network which does not support mtu>1600)

However, the reason for the reprovisioning is still a mystery to us.

We have another customer running CSC and the other day, their router hang. After they reboot their router (7206), we can ping to their CE but their VPN failed until we reprovisioned (not by deploying service request).

We encountered a few cases on this.


Re: Reprovisioning of customer's VRF for CSC connections

I am not clear with your question.

AFAIK SONET/SDH MTU would be 4470 and your question actually fails to convey that restriction.


May be you should consider opening a TAC case with Cisco.


Re: Reprovisioning of customer's VRF for CSC connections

Ok, let me explain this.

In CSC mode, you can exchange the labels with the Customer Carrier using LDP or BGP.

Now since you mention you are using LDP which BGP is flapping. The Customer Carrier would run only MPBGP with his remote site directly. And he wont run BGP with you as you act like his "P" router. So he just using the IGP with you for running his end-to-end MPBGP.

So i meant i did not get your question, when you say there was a MTU mismatch on SDH for BGP session.

If you have more details about the case like any captures etc, that could be looked at.

Akso TM is providing CSC service? I wasnt aware of this, as we were a part of TM MPLS and also personally a part of TM Metro-Triple Play rollout with the CIsco team.



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