Appendix C: Aastra Phones as external extensions

This assumes the Asterisk server is configured for external extensions and the extension configuration in asterisk is configured to be used as an external extension.  Both are described earlier in this guide(sip_nat.conf, nat=yes).

Reset the phone to factory defaults.  All you need to configure in the phone are phone number, callerID, authentication name, password, Proxy IP and Registrar IP.  Leave everything else at default and it should work.  I also changed registration retry timer and BLF subscription period to 120s.