1. A full cone NAT is one where all requests from the same internal IP address and port are mapped to the same external IP address and port. Any external host can send a packet to the internal host, by sending a packet to the mapped external address.

2. A restricted cone NAT is the same as a full cone NAT except an external host can send a packet to the internal host only if the internal host had previously sent a packet to the external host IP address.

3. A port restricted cone NAT is like a restricted cone NAT, but the restriction includes port numbers. (extenal host IP address and port number)

4. A symmetric NAT is one where all requests from the same internal IP address and port, to a specific destination IP address and port, are mapped to the same external IP address and port. If the same host sends a packet with the same source address and port, but to a different destination, a different mapping is used. Furthermore, only the external host that receives a packet can send a UDP packet back to the internal host.

This entry was posted on Tuesday, March 31st, 2009 at 12:09 am and is filed under Voip. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.