please help to verify the simple firewall rules is ok for the call testing of my VOIP telephony syst

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http://www.unix.com – Dear Sir, I want to test the VOIP Telephony system installed in a IP PBX server behind a NAT router. This NAT router connects to a modem (with NAT as well), and then the modem (with static public IP assigned by the ISP, e.g. directly connects to the Internet. There are several IP phones connect to the IP PBX server. The NAT router is configured as DHCP, and as a gateway (e.g. also for the LAN (the NAT router, the IP PBX server and the IP phones consist this LAN). The IP PBX server and the IP phones all connect to the ports of the NAT router, and are with sta (HowTos)