After many days of struggling, it appears to me that the UPnP function of amule is not working. The uTorrent and eMule clients running on my Windows 7 PC have no problem setting up port UPnP-PMP as shown in the Tomato web UI. The port forwarding page in Tomato UI somehow does not work with 192.168.1.1. So I tried to manually setup port forwarding by following the thread (http://forum.amule.org/index.php?topic=18427.5;wap2) using iptables command, and finally got an high ID. However, the Kad network still cannot connect, and amule still does not download (0kB/s down speed).
Any help is appreciated. I really like to use my WL-520GU as a amule downloader to save me lots of electricity. Thanks!