T1 errors, drops - Cisco
Posted on 2009-02-09
Ok, this is a really strange one... I have a Location A which has three T1s from the same telco (Windstream, formerly Alltel). Two are point to point and one is a PRI. One of the point to point T1s is taking a lot of errors, inconsistently, and dropping. It comes right back up and the cycle continues. The telco is providing clock from the CO to both ends of this circuit. So, both ends are configured to take clock from the line. The circuit will run clean for hours or days, then the error rate goes through the roof and it it'll bounce for a while. The telco has been out to test both ends several times, as well as testing intrusively twice for two hours. No errors from smartjack to smartjack. Last week I called and the tech was out again monitoring at the smartjack at Location A with a tbird. He was seeing errors coming from the router on the Site A side, and none from Site B. While we were talking, we both saw the linecode indicator on the tbird flash back and forth between AMI and B8ZS. It changed pretty rapidly for a few seconds, then settled back to B8ZS which it is supposed to be. How is this possible, and what do I do about it?
Location A Equipment:
Cisco 2821 ISR
VWIC-2MFT-T1 (PRI and the other point-to-point)
WIC-1T (the T1 in question)
KENTROX CSU/DSU, v.35 cable
Location B Equipment:
Cisco 2811 ISR
VWIC-1MFT-T1 (the T1 in question)
Here's what I've done so far:
1. Changed equipment. I've tried this T1 on both the WIC controller and the external DSU.
2. Changed clock source. I've tried line/line, line/internal, internal/line. Haven't tried internal/internal 'cuz you know that wouldn't work...
3. Ran a temporary cable from the DSU to the smartjack to make sure it wasn't the building wiring. No change.
I'm really out of ideas. I've changed everything at Location A, and everything but the wiring at Location B. The telco insists the circuit is clean and that it is my equipment. After seeing those results on the tbird last week, I'm convinced, but HOW IS THIS POSSIBLE?? The other two T1s run completely clean at that location, on the same equipment that has been tried on the problem T1. I don't use line build out settings on the other T1s. All are ESF/B8ZS. All the equipment has been working in that location or other locations. We run VoIP over this link and it causes quite the headache for Location B when they have no phone service when the circuit drops.
Any help is very greatly, truly appreciated!