SIP server inside
For various reasons, you might want to use a separate SIP server instead of the built-in server in the firewall. That SIP server would be located on the inside or maybe on a DMZ.
If the SIP server is located on a NATed network, DNS queries for the SIP domain should point to the firewall, which in turn will forward the SIP traffic to the server.
Here are the settings needed for this. It is assumed that the firewall already has a network configuration. Only the additional SIP settings are listed.
Basic
Go to the Basic page under SIP and turn the SIP module on. Here you also select log classes for SIP event logging.
Routing
If the SIP server is located on a NATed network, all SIP traffic from the outside will be directed to the firewall, which must know where to forward it.
One way to do this is to enter the SIP domain in the Static forwarding table on the Routing page, to link the SIP server IP address to the name. The firewall will look up the domain here instead of in the DNS server, and send the SIP traffic to the correct IP address.
Filtering
On the Filtering page, you set the Default policy for requests under Proxy rules to Process all. This means that the firewall will process all SIP requests regardless of which SIP domain they are bound to.
Interoperability
If Windows Messenger is used for SIP communication, you need to set a parameter on the Interoperability page. Set lr=true status to On under Loose routing.
If the SIP server is an LCS (Live Communications Server) or some other server that does not accept more than one Via header in SIP packets, you must enter the SIP server IP address in the Remove VIA headers table. This will make the firewall strip SIP packets of extra Via headers when it sends those packets to the server, and add the Via headers when the response packets are received.
Basic Configuration
If no Outbound proxy is entered, the firewall must be able to look up SIP domains in DNS. DNS servers are entered on the Basic Configuration page under Basic Configuration.
Save/Load Configuration
Finally, go to the Save/Load Configuration page under Administration and apply the new settings by pressing Apply configuration.
