Interesting problem

[lgoldberg]

Installed two Internet T1 connections. One with New Edge (MCI) and one with Qwest wholesale. In both cases, my Cisco 1720s do not work. In both cases, they work when an Adtran external TSU is connected to the jack and then serial port is connected to Cisco router.

Stumped. Any thoughts?

[jackyoung]

It seems to be a hardware issue that connect an external device works. Could you please provide the config. of the router ?

Do you mean the Adtran external TSU is a MUX ?

What interface of TSU connect to the T1 ? Do you confirm you are using the correct cable for Cisco ?

Hope this helps.

[lgoldberg]

We've been stuck for a week.

Tried three routers (two 1720s and a 2600) all work on Cu T1s but not on T1 muxed from OC3 with Adtran MX. When Adtran external TSU is connected to router and then to MUX, all is fine. Wiring is all checked out. Cable is E1T1 (1,2,4,5).

[jackyoung]

As you said, it is a muxed connection. It certainly works w/ a MUX. The serial of 1720 cannot suppotr MUX, and 2600 require an IMA module.

http://www.cisco.com/en/US/products/hw/routers/ps259/products_data_sheet09186a00801aa726.html

However, please try to consult w/ the PTT or the MUX provider for the compatibility of CIsco IMA module and the remote end MUX device.

Hope this helps.