Polycom 4300T manual Data Networking Configuration, NAT for Data Traffic

User Guide V2IU 4300T Converged Network Appliance

Data Networking Configuration

The 4300T provides static IP routing and two types of Network Address Translation (NAT) functions for data traffic. This section describes the use and configuration of these features.

NAT for Data Traffic

NAT allows hosts on a private internal network (the LAN side of the 4300T) to anonymously communicate with devices on an external network (the WAN side of the 4300T). The 4300T with NAT enabled will re-write outbound packet headers using public IP addresses in place of private IP addresses so that the private IP addresses are not exposed to the external network. Additionally, the ports used by the IP addresses are also changed as they traverse the 4300T. This is known as Port Address Translation (PAT) and provides an additional security measure. The 4300T maintains a table of these mappings so that return packets can be forwarded to the correct host on the private network.

The 4300T provides two types of NAT functions: dynamic NAT and static NAT. Dynamic NAT allows many private IP addresses to be mapped to a single public IP address (using different port numbers of the public IP address). Static NAT maps private IP addresses and port. For example, mapping a public IP address to a specific machine on the private network responsible for receiving email.

Note The 4300T ALG automatically handles NAT for voice devices.

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