atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's T1 drop/insert (add/drop); Cisco lock-up

I have a P2P T1 between 2 locations, Mitel SX2000 for the A-end, SX200 is Z-end. Using channels 19-24 for digital E&M. When circuit is up direct from CSU to PBX, all is well. When Cisco 1841s are placed at both ends, the voice circuits lock-up after a few minutes (data flow is fine).

Clock source is primary on the A-end, internal on the Z-end.

Does anyone have other sample IOS configs I might compare to? Thanks!

I don't know Cisco or their terminology. On most systems the Clock is master and slave, internal would be just that an internal clock source. So if this is like other T1 equipment you are using two timing sources and it won't work.

If it's a real telco T1, you want their clocking on both ends, don't try to clock the circuit yourself.

Post says he has a switch at both ends. Telco to a PBX you slave off Telco.

Can you please give me a little more info about how the routers come into play? I'm assuming the T1 goes into the CSU then to the router? If so, what device are you using to peel off voice channels to the pbx or is there an FT1 port on the Cisco? How is the cisco configured and what cards / modules are in it?

Yes, I see he has a PBX at each end. If this is a point to point LEC T1 it will be providing clock to each end. If it's just two pairs of wire then you will clock one end yourself.

The lec doesn't provide timing on a private line T-1. Hasn't in years and then you had to pay for it.

You have to make sure that SX 200 has a Stratum 4 as a clock but not a Stratum 3 cause Str.3 is more acurate and to have them both on 2 ends is not very good. Can goes out of sink. Go in Maintenance on SX 200 and look at the Link status. And do not make a clock as an Internal on Z side.

Majestic,

if this does not format well i can send an image:

how it's working now:
lan-->csu-->router-->span<--router<--csu--<lan

| |
pbxt1 pbxt1
-dsx- -dsx-

what we were shooting for ;circuits sync ok, no frame or code errors but the e&m side of the sx2000 lockout right away.

lan-->-->router-->span<--router<--<lan

| |
pbxt1 pbxt1
-csu- -csu-

In other words, we're now doing the add/drop *before* the router, we'd like to do it from *in* the router.

snip of router config for add/drop:
controller T1 0/0
framing sf
crc-threshold 320
clock source line primary
linecode ami
cablelength short 133
channel-group1 timeslots 1-18
tdm-group 2 timeslots 19-24 type e&m
description ** P2P **
!
controller T1 0/1
framing sf
crc-threshold 320
clocksource internal
linecode ami
cablelength short 133
tdm-group 3 timeslots 19-24 type e&m
description ** to mitel **

You can only have ONE clock source, period.