IX. NAT Related Features

In the previous section, we discussed port mapping to allow internal network devices (e.g. servers) to be accessible from the Internet. The Vigor router actually supports three variants of port mapping methods, as follows :

1. Port Redirection - The packet is forwarded onto a specific local PC if the port number matches that defined. You can also translate the port to another port locally.
2. Open Ports - As Port Redirection (above) but allows you to define a range of ports.
3. DMZ Host - This opens up a single PC completely. All incoming packets will be forwarded onto the PC with the local IP address you set. The only exceptions are packets received in response to outgoing requests from other local PCs or incoming packets which match rules in the other two methods.

When using combinations of these three systems, there is a priority structure; i.e. if a rule in one method co-incides with a rule in another method, then there is strict precidence, so that the result should be predictable. The precidence is as follows :

Port Redirection > Open Ports > DMZ

For example, if an incoming packet's port number matches a rule in both 'Port Redirection' and 'Open Ports' then the packet will be forwarded onto the local address defined in 'Port Redirection'.

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