no ringback tone...succession

[deelee74]

I have a customer with 2 option 11's connected via virtual IP trunks. The switches are in the same building. PBX #1 is maxed out, and PBX #2 is going to be used to add more phones to the site.
Both switches have a signalling server and 1 media card each.
My problem is that when you call an extension on the PBX #2 through the auto attendant (which is on a remote 81C), you do not get a ringback tone and the caller thinks that the PBX hung up on them.

Tracing the route of a call, I see that it comes in on a ground-start, unsupervised trunk on PBX #1...it routes to the 81c over a PRI....the auto-attendant answers....you key in the DN of a phone on the PBX #2...the voicemail flashes and routes the call back to PBX #1 over the same route. PBX #1 sends the call to PBX #2 through the IP connection. The phone on PBX #2 rings, but the calling party can't hear ringback.



NOW!!
if you call from PBX #1 to the phone on PBX#2 over intercom dial tone, you can hear ringback.
Also, if you use intercom dial tone to call the auto-attendant's route number, you can transfer yourself back to PBX#2 and you hear ringback.

You only experience the problem when calling into the groung-start COT.

Any suggestions of how to fix this...or does anyone have an explanation of what is happening here?
Our tech support guy says that he believes that since we are not using ISDN, then there is no way to send a ringback request to PBX #2 over IP. As far as PBX #2 knows, it is just supposed to terminate the call on its telephone set.

Any comments, suggestions or miracles?

 

[acewarlock]

Why do you go from PBX #1 to 81C then back to PBX #1 then to PBX #2. is there any reason you can't just go from PBX #1 to PBX #2?

 

[deelee74]

Well, the company is a large healthcare organization that has the 81c at the largest hospital acting as a sort-of central hub for all of their smaller switches.

Every incoming call to each of the hospitals is set to auto-terminate to the auto attendant on the option 81.

Each option 11 (except for the new option 11 #2) has a dedicated PRI that ties it to the 81. So until all of the switches are IP enabled (which is the plan), any incoming call goes straight over PRI to the central voicemail's auto attendant and out to whichever switch has the DN they are looking for...in this case, it has to go back to Option 11 #1 because through it is the only route to option 11 #2.

Option 11 #2 is not its own site. It is the customer's way of not having to change out the maxed out option 11 with a 61.

 

[acewarlock]

So if the 81C goes down, nobody can get a call?

 

[dlesap]

That's a h323 protocol misunderstood between both PBX. You will have to trace call in SigServ to see where it fails.

 

[deelee74]

We don't maintain this PBX. We are only involved in upgrading the switches to succession and getting everything up and running properly. The hospital's clinical engineering department maintains it. The department is staffed 24 hours a day, so if the 81C goes down, there is someone there whose job is to remote into each 11C and change the ATDN from the voicemail on the 81C to phones at each hospitals' information desks.

They can get calls. They just can't transfer between switches and they have to call through the PSTN to reach DNs at other sites.

Lucky for them, the 81C has never gone down in its 10+ years.

 

[deelee74]

GETTING BACK ON TOPIC!!!!!



This problem still exists, but it looks like I have narrowed it down to a specific point.
When the call is bounced back from the Meridian mail, PBX #1 sets up a separate call path to PBX #2, essentially putting the caller on hold until someone answers at PBX #2. Then when the call is answered, the 2 paths are connected and the call proceeds.

Is there a way to stop this? We essentially need to establish Anti-tromboning on the IP link between the 2 switches so that the caller is connected throughout the entire path of the call.

 

[dlesap]

Log on SS PBX2 with admin1 level pwd.
Turn on H323 Call trace on it.
Make a call and look your terminal.

Then, do the same with PBX1 and compare where is the difference. I guess the answer is in the analyze

 

[acewarlock]

If you have MOH applied to this route, then they would hear music.