I have got an alcatel IP phone at remotes sites and an IPBX at the main site. The IP phones can register and can call the main site. The firewall rules allows all trafic from remote sites to HQ and not between them.
However, the IP phones cannot talk with each other. I want just to allow the protocols that Alcatel IP phones use in my Cisco Router ACL for IP phones to communicate between them as far as remote sites are concerned.
Does anybody have a clue? I may not sure if it is SIP or some other proprietary protocol of some sort.