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Is it a simple procedure to configure ISA Server 2000 to allow an Asterisk IPPBX connect to SIP provider. On asterisk forums they say the ISA has difficulties handling SIP, softphones that i have installed behind the firewall work fine with the provider when the firewall client is installed on the workstation. With asterisk being a linux based system this will not be an option. Is the config a matter setting up port forwarding, is this a more complicated task on ISA server than just selecting the ports i need and then the ip of the internal machine i want to forward them to?

UPDATE: I dont think this is possible from what ive researched



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I've managed to get a Trixbox server working behind ISA2004 with external SIP phones (but I haven;t attempted a SIP trunk). It took a lot of fiddling but it does work. However, I would recommend that you find a VoIP provider that supports IAX trunks, IAX is much more robust in the face of NAT firewalls.

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