UC500.com

I'm trying to setup uc520 to work with my Vonage softphone account. I've configured sip-ua to registrater ok and incoming calls work - but I can't make outbound calls. I think it's because I need to authenticate the dial-peer when it makes a call.

I seem to recall that on another CME system - there was an authentication command under the dial-peer. Does UC500 support this command?

Perhaps a newer IOS? I'm running 12.4(11)XW3

Thanks in Advance