Subnet forwarding is commonly used when servers with public addresses are placed behind the system. Configuring the network in this way allows the system to manage and prioritize bandwidth, sharing it between the VoIP services and the servers.
When pass-through traffic is allowed, it is common for one address from the forwarded range of addresses to be assigned to the rule output interface. The system uses this address to act as a gateway router for the subnet. The address is assigned using the Network > Subinterfaces page. Refer to Configuring Subinterfaces.
The subnet and pass-through addresses are not protected by the firewall.
A similar method for forwarding traffic is provided by Proxy ARP. Proxy ARP is used to “bridge” addresses within a single subnet range from one interface to another. Often this is used to bridge and forward a public address to the protected side of the system without having to subnet the public address range. Proxy ARP does not require an additional gateway address on the System for the subnet, but does not allow port and protocol filtering for pass-through traffic. Choose Network > Proxy ARP and refer to Configuring Proxy ARP.