Reference Manual

NAME

umap - maintain the UDP Port Table

umap [add|delete dst_port_range [src_port]]

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Command umap is used to add or delete UDP port numbers used by applications such as ICQ (port 4000) and Battle Net (port 6112).

Umap with no arguments prints the current contents of the UDP Port Table.

NAT32 handles mapping of UDP packets sent to the Internet on ports in the UDP Port Table as follows:

• If the Destination Port Number of a UDP packet is listed in the UDP Port Table, then make the port mapping for that combination of Destination Port and Source Port Numbers permanent. Otherwise, give the port mapping a time-to-live of 60 seconds.
• If the Source Port Number of a UDP packet is listed in the UDP Port Table, then make the source port number permanent. Otherwise, calculate a new source port number in the usual way.
• If the Source Port Number is 1, preserve the original Source Port Number in the packet.

This mechanism allows UDP applications which rely on port mappings to be permanent (e.g. ICQ, Battle Net and others) to function correctly on machines behind the  NAT32 gateway.

Note that the mechanism differs from the Permanent Port Mapping Mechanism in the following way:

• Permanent Port Mappings map incoming, unsolicited packets to one fixed machine on the private LAN.
• The umap mechanism is needed only for applications which continually send UDP packets to a given Server.

Games which use Battle Net often require that the source port number of UDP packets be preserved. Such games usually use the same source and destination port number (6112). Also note that a ppmap command is still needed, because unsolicited UDP packets are constantly being sent to the machine running the game.
The following ppmap command could be used:

ppmap add udp 6112 IP_Addr 6112

Games which send a continual stream of UDP packets from an unknown source port to a fixed destination port could use the following umap commands to preserve the source port number:

umap add 9000 1
umap add 9001 1

pmap, ppmap, setb