Action Src Interface Src Network Dest Interface Dest Network
OutboundToProxy NAT lan lannet dmz ip_proxy
OutboundFromProxy Allow dmz ip_proxy wan all-nets
InboundFromProxy Allow dmz ip_proxy core dmz_ip
InboundToProxy Allow wan all-nets dmz ip_proxy
With Record-Route disabled, the following IP rules must be added to those above:
Action Src Interface Src Network Dest Interface Dest Network
OutboundBypassProxy NAT lan lannet wan all-nets
InboundBypassProxy Allow wan all-nets core ipdmz
Solution B - Without NAT
The setup steps are as follows:
1. Define a single SIP ALG object using the options described above.
2. Define a Service object which is associated with the SIP ALG object. The service should have:
• Destination Port set to 5060 (the default SIP signalling port)
• Type set to TCP/UDP
3. Define four rules in the IP rule set:
• An Allow rule for outbound traffic from the clients on the internal network to the proxy
located on the DMZ interface.
• An Allow rule for outbound traffic from the proxy behind the DMZ interface to the remote
clients on the Internet.
• An Allow rule for inbound SIP traffic from the SIP proxy behind the DMZ interface to the
clients located on the local, protected network.
• An Allow rule for inbound SIP traffic from clients and proxies on the Internet to the proxy
behind the DMZ interface.
4. If Record-Route is not enabled at the proxy, direct exchange of SIP messages must also be
allowed between clients, bypassing the proxy. The following two additional rules are therefore
needed when Record-Route is disabled:
• An Allow rule for outbound traffic from the clients on the local network to the external
clients and proxies on the Internet.
• An Allow rule for inbound SIP traffic from the Internet to clients on the local network.
The IP rules with Record-Route enabled are:
Action Src Interface Src Network Dest Interface Dest Network
OutboundToProxy Allow lan lannet dmz ip_proxy
OutboundFromProxy Allow dmz ip_proxy lan lannet
InboundFromProxy Allow dmz ip_proxy core dmz_ip
InboundToProxy Allow wan all-nets dmz ip_proxy
With Record-Route disabled, the following IP rules must be added to those above:
Action Src Interface Src Network Dest Interface Dest Network
OutboundBypassProxy Allow lan lannet wan all-nets
6.2.8. The SIP ALG Chapter 6. Security Mechanisms
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