Polycom 4300T Benutzerhandbuch

User Guide V

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IU 4300T Converged Network Appliance

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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 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.  

The 4300T ALG automatically handles NAT for voice devices.