[HELP] Error messeage when trying to call Cisco SIP box

This will definitely not be a typical setup, but I am hoping someone can point me in the right direction.

I have setup Asterisk on my linkSys WRT54G using OpenWRT. Asterisk runs well, and I can register and call from two different machines using softphones.

Here is where the problems start. I have a Cisco 3620 router with an NM-2V module with a two port FXS card installed. I have a fax machine, and an analogue phone attached to these two ports. I have configured the router to use SIP, and have configured the extensions.conf and sip.conf using host=[ip address of 3620] since there is no IOS version for this box that will request SIP-server registration.

Everything works as expected, except for the fact that I cannot call in to the FXS ports on the router. The FXS ports are configured correctly a I can call from one port to the other. I can call out through Asterisk no problem to the softphone already registerred with Asterisk, but when I try to dial the routers FXS extension, I get the following error (as seen on asterisk):

– Called 2003
– Got SIP response 400 “Bad Request - ‘Malformed/Missing URL’” back from
– SIP/2003-ca11 is circuit-busy

I have run debug on the router, and can see that the router is making this response to the Asterisk, but cannot seem to figure out where the problem lies.

Any ideas wold be greatly appreciated.

Regards to all,