Thanks again Andrey. I'll see if my guy can try the loopback test tomorrow and I'll post the results. However, I am a little concerned about the answers.
If the line isn't the problem, and it's a low probability that it's a cisco hardware problem, then the problem probably lies with the telco. If that's the case, what could be causing the problem at the telco? Just curious. Thanks again for all the help.
From the highest to lowest probability -
Check the cable first, worry about telco later :-)
Regards, Andrey.
If the LCVs and PCVs are increasing, thats your biggest problem.
In a straight-up point-to-point T1 circuit, the telco doesn't provide clock. The clocking comes from RouterA's 'clock internal' statement. In your setup you need one side to provide clocking, and one side to sync to it. (ie. clock internal vs clock line).
That shouldn't do anything different. Clocking issues will just get you slips and if the slips get bad enough, and occasional line protocol down.
If you are incrementing LCVs and PCVs, then you have something lower than worry about the clocking. Clocking doesn't affect these at *all*.
One of your routers needs to originate clock, one needs to sync to that clock. If you do both set to line, they'll try to sync to whatever the other is doing, but you will have slips eventually. Clock slips mostly show up on voice circuits with odd digital noises and things. In data circuits, if it continues on enough, you can take a line protocol hit from time to time, but most times will work fine.
In my experience, this sort of issue is going to be something bad in the CO, a bad smartjack card, or bad wiring. At the small end of probability is a bad CSU/DSU on your T1 interface. At zero probability is the router. The CSU/DSU is much more likely a culpret than the router, but this looks more like a cable or CO issue. Replacing the router while retaining the CSU/DSU will most likely do nothing for you.
I don't think so, other than replacing the cable may bypass bad wiring. The ABAM cable won't be so much better, it'll just be different copper pairs, which you could probably do by switching to different house pairs.
Unlikely. More likely is a CO or cabling issue.
Thanks. What is the difference between this cable and a standard cat5? Is this one basically a cat3 with less twists that a cat5?
The main difference with the ABAM cabling is that each pair is individually shielded, and it uses 22AWG copper inside (which can be a problem if you are punching this down into anything, 66-blocks will take the 22AWG, but patch panels, 110's or Krone/BIX won't take the
22AWG wire, it'll be too big, it was designed for screw terminals).A real of Beldon 7838A is around $460.
I also don't know of any that have Plenum jackets, which could very well be an issue, 7838A is PVC, and the stuff I've seen in the field is as well. You may run into fire codes preventing its use.
Weird, my newsgroup access has been down for a couple of days. Anyway, we replaced some hardware and nothing changed.
Andrey, I'm going to take your advice and perform the loopback testing. I probably won't be able to test the problem router for a couple of days, but will post the results when I do. Right now, I need to read up on how to do loopback testing. 8-)
What loopback tests should I perform? If I unplug RouterB and plugin the loopback there, and run an extended ping from RouterA through the loopback, and everything works fine, this verifies that my problem is either my long cable or some type of hardware failure with my cisco device (either router but more likely csu/dsu card) right?
If that loopback test fails, this means the problem exist with the Telco wiring right?
What are the extended ping commands that I should use for this test and what am I looking for? Thanks again for all your help!
Correct.
Wiring, configuration, repeaters, etc.
Ping with 0x0000, 0xFFFF, 0x4040 and 0x8000 patterns. Tell us if any of them fail.
Very good source of information about T1 circuits is T1 A Survival Guide by Matthew S. Gast.
Regards, Andrey.
Thanks. I'll post the results. I also just ordered the book you suggested. I do have one last (I hope the last) question though:
If I plug in my loopback wire into the smartjack where routerB is located, and perform the ping test from RouterA, and everything works fine, then the problem isn't with my Telco.
From here, I would like to verify that the problem is with the long cat5 cable and not with RouterB. To test this, I was thinking I could plug in a short cable from the smartjack to RouterB, configure RouterB to have a software loopback, and then run the ping test again from RouterA. If all of that works fine, I'll do the same software loopback test from RouterA, but with the long cable from the RouterB smartjack to RouterB. If there are errors, then it's definately the line.
Anyway, I have a question about configuring RouterB for the loopback. If I go into my serial interface configuration: RouterB(config-if)#
There is a loopback command: RouterB(config-if)#loopback
From here, there are several options: RouterB(config-if)#loopback dte RouterB(config-if)#loopback line RouterB(config-if)#loopback remote
I think the command that I want to just test the circuit from RouterA to RouterB (without going through the CSU/DSU card [which will just test the external line]) is: RouterB(config-if)#loopback line payload
Is this correct? If it is, then can I just run the same test you suggested earlier to test the line?
Thanks again. Huge help.
Well, if you can drag RouterB close enough to smartjack to bypass your Cat5 cable, you can just run those patterns between the routers. No need for loopback.
Regards, Andrey.
Hey guys,
Thanks for all of the help on this problem. We were finally able to coordinate with the ISP correctly and they determined that the problem was on their line back to the CO.
Thanks again. John
Cabling-Design.com Forums website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.