Install Tomato USB over DD-WRT on Linksys WRT310N v2

1) Read the document on http://www.polarcloud.com/tomatofaq

2) Enable Telnet Client on Windows 7

Start
Control Panel
Programs And Features
Turn Windows features on or off
Check Telnet Client
Hit OK

3) Check Network Gateway IP address
ipconfig

4) Telnet into DD-WRT router to get DD-WRT password
telnet into the router 192.168.1.1 *before* upgrading and type "nvram get http_passwd". The result will be your password in Tomato. This is necessary because of a change in DD-WRT's way of using the standard http_passwd variable

username: root
password: web interface password (default is admin)

5) Find appropriate Tomato USB build
Check http://tomatousb.org/doc:build-types

For my Linksys WRT310N v2, The CPU is MIPS R2 and build type is NoUSB-Std (4MB flash)
go to download page http://www.tomatousb.org/download the download link is http://sourceforge.net/projects/tomatousb/files/Experimental%20%28beta%29/K26-MIPSR2/tomato-K26-1.28.9054MIPSR2-beta-Std.rar/download

6) Use upgrade firmware page in DD-WRT to install Tomato USB firmware