SIP phones do not hangup when used inside LAN


#1

I am using GXP2000s and Budgetones with Asterisk@Home with asterisk 1.2 inside a LAN. It is connected to internet using an ADSL router/modem. I have two asterisk servers, one inside the LAN and the other in the public internet. I can get the SIP phones(inside the LAN) get registered with both asterisk servers and start calls. But when used with the asterisk server inside the LAN, the call does not hangup even after the receiver is put down. But when used with the Asterisk server in the internet this does not happen.
Also I have tried using an IAX softphone inside the LAN and it works fine. So it seems to be an issue with SIP protocol and traffic routing inside the LAN.

The router is Prolink Hurricane 9000P , no firewalls

Hope someone can help me in this regard. I have tried so hard to solve this issue.