User Guide

84 Chapter 4. Configuring Special Features
first private port:
if specified, this is a port remapping of the incoming request from the remote end.
first port
maps to
first private port.
first port
+ 1 maps to
first private port
+ 1
last port
maps to
first private port
+
last port
-
first port
first port
through
last port
are the ports as seen by the remote end.
first private port
through
first private port
+
last port
-
first port
are the equivalent ports the server on
your local LAN will receive the request.
Remember to type
save
to make the changes persistent across boots.
Examples:
system addserver 192.168.1.5 tcp smtp
system addserver 192.168.1.6 tcp 0
system addserver 192.168.1.6 udp 0
The router sends a server request for SMTP to 192.168.1.5 when such a request comes from any remote
router running NAT. The router sends any other server request (tcp or udp) to 192.168.1.6.
!
!!
!
Server Request Hierarchy
When handling a request from a remote router (to which the local router has NAT enabled), the local
router selects a server based on the following priority algorithm:
1.
remote addserver
— The local router selects a server for the remote router that handles that
particular protocol/port.
2.
system addserver
— The local router selects a global server that handles that particular protocol/
port.
3.
remote addserver
with
port
0 — The local router selects a server for the remote router that handles
that particular protocol (such as tcp/udp) and
any
port.
4.
system addserver
with
port
0 — The local router selects a global server that handles that particular
protocol and
any
port.
5. If an IP address is used for true NAT host remapping as well as for IP address/port translation, the IP
address of the local remapped host as the server is selected.
6. Router’s
IP address
— The local router selects itself (the local router) as the server.
Classic NAT
With classic NAT, one PC IP address is translated to one NAT IP address. This NAT technique is primarily used
to make certain hosts on a private LAN globally visible and give them the ability to remap these IP addresses as
well.