Cable Forum - Cool Bandwidth Monitor for WRT54G/GS Routers...

After searching for a decent bandwidth monitor I came across WRTbwlog (screenshots) which is cool because a) it runs on the router, not your pc, and b) it can monitor just the WAN port so local data isn't included giving a false reading.

First off, this doesn't run on the official firmware. You'll need to be running DD-WRT (which I highly recommend), Talisman or something else that includes awk. It's installed by telnetting into your router and typing a few simple lines.

The features include...

You can set a billing date for data usage, rather than monthly totals.
Monitor and display the total internet traffic of all wired and wireless clients connected to a Linksys WRT54G(S) router.
Monitor, which computers are using your wireless network.
Start custom scripts, if the traffic exceeds certain limits or if unauthorized clients are detected on the nework.
Easily upload, create, modify and delete files and NVRAM parameters on your WRT54G(S).
View loads of information about your WRT54G(S).
Scan the WLAN frequency range for other WLAN devices or interference.

The only downside is that when you reboot the router the data and settings are lost, although there is an automatic backup option which you can set.

WRTbwlog is definatly worth a try. :)

Andy.