Buffalo WHR-G54S Supplementary Manual page 4

Now, you need to configure the second AirStation with the MAC address of the first
one. In your browser's address field, enter "192.168.11.100". This will take you into
the Web-Based Configuration Utility for the second AirStation.
Once again, the username is "root" and the password is blank.
In the Web-Based Configuration Utility, click on the Advanced tab, select Wireless
Config, and choose Basic. Change the wireless channel to match the one you
set for the first AirStation. Change Framebursting from 125 High Speed Mode to
Framebursting or Do not use (whichever you chose for the first AirStation). For easy
roaming, you may change the SSID to match the current SSID setting of the other
AirStation. Click Apply. Your AirStation will reboot in 30-60 seconds.
Now, under Wireless Config, choose Repeater.
Confirm that Repeater-Bridge (WDS) is set to Enable. Click Edit Registered WDS
Partners.