T1 Clocking Problem

[h.parsons]

I am having a lot of input errors on my point to point T1, I suspect a clocking problem. I was told that the telco was not providing the clocking so I set one router source to internal and the other to line.This made things worse. I then set both to line which for now seems to help. Is there a way to see if the telco is doing the clocking? If I do a show controllers I see that TX and RX clocks detected.

[scottmac]

If the Telco wasn't providing clock, then it wouldn't work at all with both set to derive / recover clock from the line.

It would be very unusual for a carrier to NOT provide clock on a standard circuit.

What kind of errors are you getting?

Good Luck

Scott

[h.parsons]

Input error's: CRC, Framing and aborts. Is the output from show controllers s0/0 > tx and rx clock detected saying that it is picking the clock off the line?

Thanks

[scottmac]

Well, first, verify the framing & line code parameters. Most often (in the US) it should be Line Coding "B8ZS" (Binary 8 Zeros Substitution and "ESF" (Extended Super Frame) framing.

If you have a provisioning sheet from your provider, read it and make sure those are the correct parameters. The alternates are "AMI" line code and SF framing (in the US).

Next, check out your cabling from the NIU/SmartJack. Bad or improper cabling can also cause those types of errors (excessive crosstalk). If the router (or CSU/DSU if you using an external unit) is near the NIU, try another cable.

You can / should also call the provider and ask them to test the circuit. They will remotely "loop" the NIU/SmartJack and send data from their edge switch to the NIU and read it back to see if it's errored. During that test, the connection to your organization will be down, but you can specify a test window for after-hours if that's a problem.

If your router (or CSU/DSU) has loopback enabled, they may also put up a loop to the CSU as well as the NIU.

If there's errors to the CSU, but not the SmartJack, then there's probably a problem with the cabling from the SmartJack to the CSU/DSU, or possibly (not likely) a hardware problem with the interface (on the router if it's an internal CSU/DSU, on the CSU/DSU if it's an external unit).

Also, don't forget to reset the counters. If you didn't reset the counters, you may be seeing old errors.

Reset the counters ("clear counters int s0/0" and confirm) and check them periodically. This should give you an idea of how bad the problem is.

This is almost certainly NOT a clocking problem. It is most likely a cabling problem (smartjack to CSU/DSU), or a carrier network problem.

Good Luck

Scott