D-Link DFL-260-IPS-12 Product Manual - Page 271
Solution A - Using NAT, Destination Port, Service, TCP/UDP, Record-Route, source, Allow
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6.2.8. The SIP ALG Chapter 6. Security Mechanisms This scenario can be implemented in two ways: • Using NAT to hide the network topology. • Without NAT so the network topology is exposed. Solution A - Using NAT Here, the proxy and the local clients are hidden behind the IP address of the NetDefend Firewall. 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 three rules in the IP rule set: • A NAT rule for outbound traffic from the local proxy and the clients on the internal network to the remote clients on, for example, the Internet. The SIP ALG will take care of all address translation needed by the NAT rule. This translation will occur both on the IP level and the application level. Neither the clients or the proxies need to be aware that the local clients are being NATed. If Record-Route is enabled on the SIP proxy, the source network of the NAT rule can include only the SIP proxy, and not the local clients. • A SAT rule for redirecting inbound SIP traffic to the private IP address of the NATed local proxy. This rule will have core as the destination interface (in other words NetDefendOS itself) since inbound traffic will be sent to the private IP address of the SIP proxy. • An Allow rule which matches the same type of traffic as the SAT rule defined in the previous step. OutboundFrom ProxyUsers InboundTo ProxyAndClients InboundTo ProxyAndClients Action NAT SAT SETDEST ip_proxy Allow Src Interface lan wan Src Network lannet (ip_proxy) all-nets Dest Interface Dest Network wan all-nets core wan_ip wan all-nets core wan_ip 271