Problems with Point-to-Point

February 14, 2007 6:42 AM

Hi, I have two Cisco 2610 routers, each with WIC-1DSU-T1 cards. We have a Point-to-Point between two locations and I am using these to route the traffic between. The lines belong to Verizon and the AdTran cards are locked in a Verizon box. I can look in and see the status lights through the top. Each location has a RJ48X loopback jack. When I plug in the Cisco at Location 1 it seems to hook up fine, and the carrier detect light pops up. (Which is strange to me because our PTP is unmonitored and I thought the CD would only come on when equipment is plugged into both ends.) Then when I go and plug in the Cisco at Location 2, I get no lights, no nothing. I check the lights in the Verizon box and an alarm is triggered with a red LED. I disconnect the Cisco and it clears the alarm. How can I figure out what the problem is? I had the company that provides the PTP come and check the circuit originally and they said they found problems but that the problems had gone away now. Is it possible that the WIC-1DSU-T1 card in this router is faulty? Any help is appreciated! Thanks.
posted by doomtop to Computers & Internet (6 answers total)

I am not a router guru, but a router acolyte.

If Site 1 is showing a carrier and Site 2 is not, then there is at least the POSSIBILITY that Verizon has a loopback or diagnostic still on the line between Site 1 and their CO/Switching station. That would make Site 1 appear to be connected, and would make Site 2 dark.

This used to happen to me on a fairly regular basis with Bellsouth PTP. They'd monitor a line to determine problems, then forget to undo their loopback, requiring another call.

Note I'm not talking about your local loopback port, I'm talking about a special loopback circuit your provider builds when performing testing on the line.

If there is no loopback at the CO, then ask them to do a test from the CO to their point of presence at Site 2 (not your router).

If that comes back clean, make sure they remove the loop (hehe) and then you may be dealing with a hardware problem.
posted by Ynoxas at 8:07 AM on February 14, 2007

You can try a loopback test:

http://www.cisco.com/warp/public/471/hard_loopback.html


Another alternative, if the routers/cards are still under warranty or you have a service contract, you can always open a service request with Cisco for them to help you to determine if you're dealing with bad hardware.
http://www.cisco.com/en/US/support/
posted by irian at 8:10 AM on February 14, 2007

If you've got a red alarm on the CSU (Adtran), it's a physical layer problem. Nothing wrong with your router.

Keep in mind that even though this is a "point-to-point" circuit, from a telco perspective it really isn't. I'm assuming this a T1, in which case the you really have two physical circuits.

Location1 < ----> Verizon < ----> Location2

In this case, the circuit (local loop) between the Telco and Location2 has a fault somewhere between your site and Verizon's CO (or there's a configuration problem on VZN's switch).

Not sure if you can talk to Verizon directly, but if so they should be able to provide you with a loopback from their switch pointing towards location 2. If the local loop is good you should see the red alarm go away and your router interface should show up/up (looped).

At a minimum, Verizon should be able to confirm that they can "loop your CSU" at both ends before they say that the end-to-end circuit is good (in which case you might have a router issue).
posted by Bluecoat93 at 8:44 AM on February 14, 2007

I dealt with this at a customer's site once, and after much annoyance it was discovered the line had been wired wrong in the phone room. I tried a cross over cable, on a whim, and the line came up fine. The telco that bought the ISP I worked for wasn't authorized to work in this customer's phone room, so we left them up with a crossover from the wall jack to the router, but with a stern recommendation to call their own phone people asap and get it resolved.

I've also seen loops left on the line (final testing often involves running a loop to be sure all is well before the routers are connected) and wics can fail, too. When I was installing T1s I used to always carry a hardware CSU/DSU in my trunk just in case the WIC crapped out. Well and an extra WIC...and several cables....and yeah, I do miss that job.

Our process was always (because it was convenient and phone companies would almost always ask for it) to swap the cables, then the wics, then call the telco that owned the circuit and have them test it while we stayed on the line. If you make your own loopback plug you can stick it in the jack and then can check for it to be sure their line's good end to end. That will eliminate bad hardware altogether sometimes.

Just throwing my two cents in.
posted by routergirl at 10:34 AM on February 14, 2007

"stick it in the jack and then THEY can check for it"
posted by routergirl at 10:34 AM on February 14, 2007

(Grr, I wish I could go back and edit comments sometimes, here)

"they said they found problems but that the problems had gone away now. "

Classic line when the telco doesn't know what the problem was and they're just hoping it's gone. It may not be. You may have to push them. Ask them what the problem was and how it was resolved, ask if they discovered a root cause, and how it was fixed, and if they can't answer that, keep pushing. (assuming you've double-checked equipment and all that stuff I said a minute ago, blah blah)
posted by routergirl at 10:40 AM on February 14, 2007