Inter IAX: incoming trunk call from Asterisk 1.4 to Asterisk 1.8 Token problem
This could be resolved by adding "requirecalltoken=no" and "calltokenoptional = 0.0.0.0/0.0.0.0" under the context "generl" of iax.conf, as shown below:
iax.conf
[general]
requirecalltoken = no
calltokenoptional = 0.0.0.0/0.0.0.0