World of Warcraft communicates on port 3724 with the TCP protocol. The patching process
requires port 3724, 6112, and 6881-6999. Once again to download the patches for World of Warcraft you
should forward the following ports.
3724 TCP 6112 TCP 6881-6999 TCP
If you can not forward ranges of ports and are only planning on having one computer playing WoW, just forward ports 3724 TCP and 6112 TCP. The 6881-6999 port range is mainly used where multiple computers on a network may be trying to play WoW at the same time.