Nokia, has very limited information and support in regards to the sip client, asterisk and nokia phones ‘took hours’ to figure out!

So, here is a working configuration, tested with Nokia 6100 Navigator and Nokia N95

Got into the Menu -> settings -> Phone Settings – > Connection -> SIP settings

Profile Name: Your desired profile name
Service Profile: IETF
Default Access Point: Your service provider access point, in my case ‘Planet 3‘
Public user name: sip:206@domain.com

Public username is in the format ’sip:ext@ip/domain’ ext is the extension setup on your asterisk server, the IP is the public IP of your asterisk server, if you do not have a static IP, use dyndns.org service.

Use Compression: No
Registration: When needed

You can set this to ‘Always On‘ if you want your sip client ready when you are

Use security: No

Proxy server

Proxy server address: sip:domain/ip
Realm: asterisk
Username: ext ‘Asterisk extention’
Password: pass ‘Asterisk extentsion password’
Allow loose routing: No
Transport type: UDP
Port: 5060

Registrar server

Registrar server address: sip:ip/domain
Realm: ip/domain
Username: ext ‘Asterisk extention’
Password: pass ‘Asterisk extentsion password’
Transport type: UDP
Port: 5060

Have fun Hopefully everything will register for you with those settings, you will need to have the appropriate ports in your router and your sip_nat.conf and sip.conf configuration corrected as  outlined in the bottom of my previous post Trixbox – External sip clients, no audio