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Carrier transitions and remote alarm on Internet router

Our Internet gateway router (Cisco 3640 w/ T1 WIC DSU card) has been logging carrier transitions on the serial interface (which is for a T1 that carries a Frame Relay circuit to our ISP). Also, I noticed the "Remote alarm" counter in "sh service-module serial0/2" increase. Routers, T1 WICs, cables, and even smartjacks have been changed out, but to no avail. Our site is dual-homed, and we are having a problem with the circuit to ISP A; no problems with ISP B. We have a router for each ISP's circuit. I know it cannot be our router because if I connect the ISP B router into ISP A's smartjack, it also starts logging carrier transitions.

Spoke with ISP A, local carrier and long-distance carriers. Variety of loopbacks were done, but all resulted in NO carrier transitions. Very puzzled and frustrated. What next? Any suggestions as to where the problem lies? Could it be a T1 timing issue?

--john

1 REPLY
New Member

Re: Carrier transitions and remote alarm on Internet router

This is one of those kind of problems that could easily burn a day's work.

Couple of things:

FIRST! Make sure that your provisioning is correct. I know this sounds elementary, but verify that you're using ESF/B8ZF (or SF etc...) and that all the channels you've paid for are provisioned. People make mistakes; have the telco double check.

1. WIC-1T-DSUs can't handle "wet" lines. Verify from your local telco that your T1 does not use sealing current.

2. Change your frame type, only for testing purposes, to HDLC when you do your loopbacks. You'll lose any frame relay configs, so make sure you have them backed up. When using HDLC, when the device is looped, it will come Up/Up and you can ping over it.

2a. First throw up a hard loop from your DMARC back to the router and see if you have problems (don't forget to take it down when you're done). Next, have the telco throw up a loop back to you from the CO. You should come Up/Up and be able to ping. Lastly, have them loop from (right in front of) the frame switch. Since you're still looped, don't change to frame relay and you should come Up/Up.

3. How many T1s are comming into this router? When you do a "sh controller" are you seeing any slip secs? Multiple T1s into a router can cause timing issues.

4. Call TAC. I can't tell you how many times I've spent hours on the phone with a customer and his provider trying to troubleshoot exactly this problem. Usually its the telco's issue and it takes a 2x4 upside the head for them to see it.

Good luck!

Mick.

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