Configure IP routing and forwarding IP Port Forwarding / Static NAT Mappings parameters
Digi TransPort WR Routers User Guide 391
IP Port Forwarding / Static NAT Mappings parameters
The router supports Network Address Translation (NAT) and Network Address and Port Translation
(NAPT). NAT or NAPT may be enabled on a particular interface such as a PPP instance. When
operating with NAT enabled, this interface has a single externally visible IP address. When sending
IP packets, the local IP addresses (for example on a local area network) are replaced by the single IP
address of the interface. The router keeps track of the local IP addresses and port numbers so that if
a matching reply packet is received, it is directed to the correct local IP address. With only one
externally visible IP address, NAT effectively prevents external computers from addressing specific
local hosts, thus providing a very basic level of “firewall” security.
Static NAT mappings allow received packets destined for particular ports to be directed to specific
local IP addresses. For example, to have a server, running on a local network, externally accessible,
a static NAT mapping would be set up using the local IP address of the server and the port number
for accessing the required service.
Configuring IP port forwarding and static NAT mapping is done by entering the following
configuration values into a table and using the Add button to add them into the NAT configuration
for the router.
External Min Port
The lowest port number to be redirected.
External Max Port
The highest port number to be redirected.
Forward to Internal IP Address a.b.c.d
The IP address to which packets containing the specified destination port number are to be
redirected.
Forward to Internal Port
The IP port number to which packets containing the specified port number are to be redirected.
When set to 0, no port remapping occurs and the router uses the original port number. The NAT
mode parameter of the appropriate interface must be set to NAPT rather than NAT or OFF for
this parameter to take effect.
Add button
Adds the port forwarding rule to the IP routing configuration.
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