Draytek Vigor 5510Gi User Manual page 57

Private IP
Private Port
Active
Note that the router has its own built-in services (servers) such as Telnet, HTTP and FTP etc.
Since the common port numbers of these services (servers) are all the same, you may need to
reset the router in order to avoid confliction.
For example, the built-in web configurator in the router is with default port 80, which may
conflict with the web server in the local network, http://192.168.1.13:80. Therefore, you need
to change the router's http port to any one other than the default port 80 to avoid
conflict, such as 8080. This can be set in the System Maintenance >>Management Setup.
You then will access the admin screen of by suffixing the IP address with 8080, e.g.,
http://192.168.1.1:8080 instead of port 80.
VigorPro5510 Series User's Guide
Specify the private IP address of the internal host providing the
service. If you choose Range as the port redirection mode, you will
see two boxes on this field. Simply type the IP address in the first
box (as the starting point). The second one is assigned
automatically after you type the private port number below.
Specify the private port number of the service offered by the
internal host. After you enter the proper number in this box, the
second box of Private IP address will be assigned accordingly.
Check this box to activate the port-mapping entry you have
defined.
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