This is a strange scenario, and all usefull advice is appreciated:

I call a Nextel cell-phone from an IP phone of my 2000IPS, and about 30% of the calls gets disconnected within 1 minute, with an error message on the cell phone something like "busy 26"

I can call other carriers' cell phones, no disconnect. I can call land-lines, no disconnect...

My first idea: Nextel coverage or network overload. Except this is impossible to test for and next to impossible to fix. Especially considering the fact, the I never get disconnected if the call comes from somewhere else. I tested it for myself. I had somebody call my Nextel from the 2000IPS, 30% of the time = disconnects. I have had a Nextel for over a year, and never got disconnected during a call. Also, during these test calls, my phone showed 5 bars for good reception.

So we think it's not Nextel.

Is it my 2000IPS? How come I can call any other land lines or other cell-phone carriers with no problem?

Here is the route a call takes to a cell phone: it goes from my IP phone into a switch, then a router, accross a T1 (about 10 miles), arrives to a router, then switch, then the LAN port on the IPS. Then the IPS sends the call out on a trunk route to AT&T (or Verizon - I don't remember)...From there on, it's just a cloud for me, and I can only guess that AT&T or Verizon then routes to call onto Nextel's network.

My other suspicion then is somehow the setup between AT&T or Verizon and Nextel is not the best (maybe their signaling is not set up ideally?) Maybe somehow Nextel's network sends a "disconnect" signal to AT&T and so to my IPS2000, and the call gets dropped, when it shouldn't.

I called Nextel customer care, and they have network engineering checking out possible coverage issues.

Other than that, I'm totally lost. But my company is using Nextels, and my executives use IP phones, so it's the top who needs this resolved, and I can't suggest for my company to switch cell-phone carrier when we have over 200 phones, and certainly I can't replace out the IPS2000 with other brand.

Anybody with any clue? Or suggestions?

Thanks, Peter