Cisco Support Community
Community Member

7206VXR/T3/Frame Relay/show int=up, down/Verizon ILEC

A long-established frame-relay T3 headend has been giving us problems lately. It looks like the T3 loses touch with the Verizon frame cloud. When I do a "show int s3/0", it's showing an up/down status. There are no errors, but I can see LMI's being sent out, but nothing returning. If I do a "shut/no shut" on s3/0, the line will return to up/up and stay up for anywhere from several hours to several days.

I've replaced the PAT3+ interface. I've replaced the router entirely, not just the chassis. The circuit has been running with no configuration changes for the last couple of years. The router is running IOS 12.1.3 and has seen no major config changes except for additional s3/0 subinterface additions as new PVC's have come on board. The coax is 336 feet to the demarc; there is a spare coax pair that behaves the same way.

Verizon has been working on the issue for 3 weeks without really having a clue. They say they don't see LMI's I believe I'm sending to them when s3/0 is up/down. I've noticed that if I keep the S3/0 subinterfaces down/down, so that all s3/0 is doing is pushing frame protocol back to the Verizon switch it seems to stay up. It's when we shove data across the wire that life gets bad. For instance, s3/0 stayed up/up for 4d16h with all the subinterfaces down/down. When I brought the subinterfaces back online, s3/0 went to up/down in 9 hours. So, data flow across the frame seems to be a part of the equation.

What might be going on here? What else can I check? How can I verify where the problem is? I don't have a frame protocol analyzer. Is there something else I can check from within IOS that will give me some clues? I don't know that Verizon is going to solve this one. Are there any troubleshooting steps I should be doing that I haven't mentioned?



Re: 7206VXR/T3/Frame Relay/show int=up, down/Verizon ILEC

When your sub interfaces are down down what is the status of the PVC inactive or deleted ? Inactive points to an issue on the remote end , deleted means that the local FR switch is not advertising your DLCI to you .

you may also do a sh interface s3/0 and look for drops in the broadcast queue .

Community Member

Re: 7206VXR/T3/Frame Relay/show int=up, down/Verizon ILEC

The PVC's show "ACTIVE", even though I have the subinterfaces administratively shutdown.

Broadcast queue is clean for the moment (no data going across the wire at all), but I'll keep an eye on it when I crank the subinterfaces back up. If I have broadcast queue drops, what is that telling me?


Re: 7206VXR/T3/Frame Relay/show int=up, down/Verizon ILEC

It is ok if the PVC are active if the sub interface is shut down .Next time they fail take notice of there status.,

The FR broadcast queue is used for LMI and routing updates , If you have a lot of drops your PVC could drop.

You may also want to check with the LEC to ensure they are not spoofing LMI .

CreatePlease to create content