Problems setting up ATA 186 with SIP Ver 3.1.0

I am a newbie who has set up Asterisk on a LAN and set up a number of softphones all working perfectly. My next step is to integrate a Cisco ATA 186 running on SIP firmware version 3.1.0. (later upgraded to 3.2.1 SIP with no change in preformance) I set it up as follows:

extensions.conf

[internal]
exten=>22299,1,Verbose(1,Extension 22299)
exten=>22299,n,Dial(SIP/ 22299,30)
exten=>22299,n,Hangup()

sip.conf

[22299]
type=friend
username=22299
caninvite=no
;host=dynamic
host=192.168.1.xxx
mailbox=22299
qualify=yes

But have encountered the following problems:

  1. If I use host=dynamic (commented out above) in sip.conf it will not register with Asterisk, but if I hardcode the (dynamic) IP address it will.

  2. When I call the phone on the ATA device, (which I can do only with the IP address hardcoded in sip.conf) the phone rings and there is communication out from the ATA phone but I hear nothing coming in. Strange! (The phone itself is OK elsewhere.)

  3. If I want to dial out from the phone on the ATA, I get a dial tone, but nothing seems to be picked up by Asterisk. There is no message on the console. After a few seconds I get a busy line signal.

What have I missed? Could it be a hardware problem?

Hi All
I am back with an update. I now have a second ATA device but of a different brand. I use exactly the same setup for it in sip. conf and extensions.conf. The new device registers its dymamic IP with Asterisk, but the old one still requires a static IP in sip.conf in order to function. Is this a harware problem or a device setup problem?