Polycom V2IU 4350 - Manual (Page 80)

User Manual V 2 IU 4350 Converged Network Appliance
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Data Networking Configuration
The 4350 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 4350) to
anonymously communicate with devices on an external network (the WAN
side of the 4350). The 4350 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 4350. This
is known as Port Address Translation (PAT) and provides an additional
security measure. The 4350 maintains a table of these mappings so that return
packets can be forwarded to the correct host on the private network.
The 4350 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 4350 ALG automatically handles NAT for voice devices.