Читаем ман по natd:
Код:
-redirect_port proto targetIP:targetPORT [-targetPORT] [aliasIP:]aliasPORT[-aliasPORT] [remoteIP[:remotePORT[-remotePORT]]]
Redirect incoming connections arriving to given port(s) to another host and port(s). Argument proto is either tcp or udp, targetIP is the desired target IP number, targetPORT is the desired target port number or range, aliasPORT is the requested port number or range, and aliasIP is the aliasing address. Arguments remoteIP and remotePORT can be used to specify the connection more accurately if necessary. The targetPORT range and aliasPORT range need not be the same numerically, but must have the same size. If remotePORT is not specified, it is assumed to be all ports. If remotePORT is specified, it must match the size of targetPORT, or be 0 (all ports).
For example, the argument
Код:
tcp inside1:telnet 6666
means that incoming TCP packets destined for port 6666 on this machine will be sent to the telnet port on the inside 1 machine.
Код:
tcp inside2:2300-2399 3300-3399
will redirect incoming connections on ports 3300-3399 to host inside2, ports 2300-2399. The mapping is 1:1 meaning port 3300 maps to 2300, 3301 maps to 2301, etc.