Cisco CUCM to Mitel 3300 call transfer issue

[jtastic]

I have a Cisco CUCM 9.1 connected to a Mitel 3300 6.0 using a sip trunk. Everything works fine except for one thing.

When I receive a call on the Cisco CUCM and then try and warm transfer it to an ACD path extension on the Mitel 3300 I run into issues. I can hear the auto attendant on the cisco phone initiating the transfer, the call from outside hears hold music from the CUCM while the cisco phone is allowed to talk (warm transfer), but as soon as push transfer again to complete the warm transfer the caller from the outside gets dead air and then in a few seconds is disconnected.

Does anyone know what the issue might be or how to resolve it.

Regards,

---Jeremy

 

[Lundah]

Sounds like a SIP setting issue, as the CUCM would probably send a re-invite to the far end to complete the transfer, and either something along the path is dropping that packets (I've seen some firewalls apply protocol handling to block re-directing a SIP call to a new endpoint), or the SIP server the CUCM is talking to does not allow the re-invite.

 

[jtastic]

I forgot to mention that I can transfer to real phone extensions on the mitel system with no issue. Its just when its to the IVR / ACD extension that I have the issue. Its the built in ACD so not a third party.

So I think that firewalls would not be an issue or transferring to extensions on the mitel from the cucm system would not work. I'm not sure if the Mitel built in IVR / ACD uses a different SIP server or where I would check that?

 

[Lundah]

I think your best bet would to grab a packet capture (.pcap file) on both the Mitel (maintenance command "sip tcpdump on" will do this, the .pcap file is stored in the /vmail folder of the controller, FTP to it and download it.) and the CUCM, then compare them for a couple of test calls. Look at the SDP packets being passed between the 2.

 

[Lundah]

And make sure you do a "sip tcpdump off" when you're done so you don't fill up the HDD with packet captures.

 

[jtastic]

Its very odd.

I run the packet capture and when I do the transfer it doesn't add a new packet capture at all. If I place a call from my phone to another phone on the mitel system it does get the info in the packet capture. When I do a transfer directly to the phone number of the ACD option it doesn't record any packet capture info, but on the phone off the Cisco system I hear all the prompts from the Mitel ACD saying I'm in the queue, and so forth?