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

Okay, here's where I'd look for a problem:

The only way that the phone system would make a difference between a call to Nextel and a call to Verizon, AT&T Wireless, T-Mobile, whatever... Is in LCR.

So check 8A4005>xxxx>zzzz where xxxx is the prefix for the Nextel phones and zzzz is the route plan that the calls follow. Is this number (zzzz) the same for nextel calls and for other wireless carriers?

If so, the the IPS is probably not the problem.
If not, then try making it the same as one of the others. Does the problem go away?
If not, then the IPS is not the problem.
If so, then you may have an issue with the trunks in the trunk group used by route plan zzzz. In fact, you probably have a problem with two-thirds of the trunks in that trunk group.

Hope that helps.

Um, stupid question: Is this only on outbound calls, or on inbound also? 'Cause that would point to a problem in an out-only trunk group...

Dear telephoneguy,

(zzzz) is the same for ALL outgoing calls. The system has one single ISDN-PRI to handle all local/long distance/International calls. No difference between different cell-phone carriers.

But you made a good point about the direction of the calls. Never though about that. I'll do more testing with that, but as I said, there is only one way to get in or out of the system.

Solved! System reset handled it. Thanks!

Oh, yeah, that's true: A system reset will sometimes correct GSW (general system weirdness).

Hey, have you backed up that database recently?