I have a small office with (3) SPA 942 units. They are attached to a Cisco E3000 router running DD-WRT v24-sp2 (04/09/11) voip. I'm running this version of DD-WRT because it includes a version of the Milkfish SIP router which compensates for the lack of SIP support on the non-VoIP DD-WRT firmware version (the non-VoIP version causes registration failures).
On the 942 units I have the outbound proxy enabled and pointed to the E3000/Milkfish Router. All works great except that you can't transfer calls.
Yesterday we added (2) SPA 504 phones. With no outbound proxy set, they work PERFECTLY, including transferring to/from the SPA 942's. Thinking I've stumbled on to something here, I removed the outbound proxy setting on the 942's. Low and behold, transfer works again. Alas, registration periodically fails.
Our VoIP provider insists the issue is with the router. And I admit this is something of an atypical network configuration (hopefully that will pique some interest here!). However, the 504's work beautifully so I don't understand why the 942's shouldn't. I'm convinced this is a phone configuration issue and not a hardware problem.
As a relatively unskilled end-user, I only have access to the web interface. I understand that if I remove the rules that pont to my providers external config file any configurations I change will be preserved. But beyond that, I know very little. So please take it easy on me.
BTW: I have discussed this with my provider and have absolute freedon to change anything I need to to make the system totally useless...
