Transfer problems with SCCP and SIP into Cisco CME

Hi all,

This would be my first post here. Not sure if it's the best place to start, but I'd imagine some of you have come across Cisco gear quite often in your VoIP travels

I'm currently setting up a slightly complicated system.

We use Asterisk at work, with Cisco SCCP phones. The SCCP driver in 1.2 isn't fantastic (crashes) and in 1.4, is even worse. So we're moving as many of our phones as possible to CME on one of our 2811's. With SCCP phones this is very simple and easy to setup. Even when we want to keep Asterisk for voicemail and CLID look-up (the DIDs still come from Grandwell over our ADSL line to the Asterisk PBX.)

My problem is migrating some of our SIP phones to CME. I'm running 12.4(11)T1 with CME 4.0(2).

These phones aren't Cisco SIP phones, however. Currently I'm working with a Grandstream. Now I think I'm correct in saying that not just *any* SIP phone is supported by Cisco's interpretation of 'SIP support', so I'm not entirely surprised that it's not working..

However, the phone can be registered and it can make calls (with some sneaky ARP tricks seeing as it's not on the same LAN segment). Calls between the SCCP phones, and more importantly, transfers between the SCCP phones and the CME SIP phone work just fine.

My problem is - when ringing from an external PSTN number, to a SCCP phone on CME .. If I transfer this to the CME SIP phone, both calls just go to hold. The call will not transfer across.

Subsequently, both calls (PSTN -> SCCP and SCCP -> SIP) are dropped a few seconds later.

SIP configuration is as below:

voice rtp send-recv
!
voice service voip
clid network-provided
supplementary-service h450.12
sip
header-passing
registrar server
no call service stop
!
voice register global
mode cme
source-address xxx.xxx.xxx.xxx port 5060
max-dn 144
max-pool 36
timezone 21
time-format 24
date-format D/M/Y
dst start Mar week 8 day Sun time 02:00
create profile sync 0381655701332147
!
voice register dn 1
number 2007
!
voice register pool 1
id mac 000B.820D.0536
number 1 dn 1
max registrations 36
dtmf-relay rtp-nte
codec g711ulaw
!

(Note there's a few things in there that I've been playing with!)

SCCP phones are configured in the standard ephone/ephone-dn way.

Any help/suggestions are greatly appreciated!