Hairpin forwarding not working with CCME 4 and SIP

[mwenger]

We are a VoIP provider and we're trying to install Cisco Unified CME 4.0 for a customer. IOS is 12.4(4)XC1 on a 2811. The customer will use our SIP service as his only outgoing trunk (no on-board ISDN or FXS cards).

On our SIP service we don't support call transfer or forwarding using the "302 Temporarily Moved" SIP method, for billing reasons. The customer needs to to hairpin routing and actually have the call go entirely through his equipment.

Following instructions, we tried enabling hairpin routing by issuing the following commands:

voice service voip

allow-connections sip to sip

no supplementary-service h450.2

no supplementary-service h450.3

supplementary-service h450.12

dial-peer voice 9000 voip

[...]

no supplementary-service h450.2

no supplementary-service h450.3

supplementary-service h450.12

Despite all this, when an ephone-dn has call forwarding enabled to an external SIP number, and a call comes in through the SIP trunk, our SIP server gets a "302 moved temporarily" message. It rejects this message and the call fails.

We even tried loopback-dn routing but we still get the same result.

Is there a way to force CCME to route the call through its inside even if it's coming and going from/to the same SIP trunk?

Thank you

-Manuel

[mwenger]

Sorry to bump this thread - could it be that what I'm trying to do is simply not possible with the current CME? Is call forward and transfer of calls coming from a SIP trunk (peer) to the same trunk only possible by using "302 moved temporarily" or "Refer-To" SIP messages, and not by having the CME router acting as a back-to-back proxy?

[davey]

sip-ua

redirect

let me know

[mwenger]

No, unfortunately it doesn't work. I have now opened a TAC case, the engineers are working on it. I suppose it will turn out to be an IOS limitation, and that a future version will fix it...

[davey]

email me off list, I have had it working on 3.4 and 4.0 in a pure SIP Enviroment, ill give you some configs.

davey@turnstone.co.nz

[skhilnan]

Email me as well if you guys cannot get this figured out. I can get one of the TMEs in my group to help out.

Sarat

[mwenger]

Just an update: Davey's post was very helpful as it solved our "call forwarding not working" problem. The solution was to add the "service session" command to my voip dial peers. CME now hairpins forwarded calls correctly.

What still doesn't work at all is call transfer. If I receive an external SIP call and want to transfer it to another external SIP number, I just get the "unable to transfer call" error message on the phone, and both calls are just placed on hold. So it's not a permission problem - the call can be dialled correctly. But when hitting "transfer" the second time, CME doesn't "know" how to join them together (ie. hairpinning).

Cisco TAC's replies so far have been quite strange. I've been told that CME does not support hairpinning and that this is still being developed - apparently not, because call forwarding *does* work now. I'm only missing call transfer, then I'm all set :-)

Thank you

-Manuel

[danm]

Any resolution? I'm having the same problem right now. 12.4.9T