We have an IPCop firewall/proxy installed in our network, and although I can use iftop to somewhat take a look at how the clients are using the Internet, is it possible to monitor it from outside the proxy with something like ntop?
Note that I'm not interested in LAN traffic, only traffic that goes to/from the Internet.
Have ntop kick out netflow data and you can get all sorts of fun reports.
http://www.ntop.org/netflow.html
http://www.networkuptime.com/tools/netflow/
Some people do just write their own flow parsers as well if you're into that sort of thing.
More information about netflow data:
http://www.manageengine.com/products/netflow/cisco-netflow.html http://www.computerperformance.co.uk/HealthCheck/netflow_monitoring.htm
We've used IPAudit http://ipaudit.sourceforge.net/. It could give you pretty granular info about outgoing/incoming bandwidth.
Here are some screenshots:
I couldn't find something that wouldn't also mix LAN traffic, so I settled for IPTraf. I do have to use it from the firewall machine, but since it's a text program it's no big deal.
By using filters and named MACs, I can quickly take a look at Internet traffic.
I also found an interesting program called EtherApe. It graphs local network connections, check it out.
Another simple monitoring tool, BandwidthD.
Cacti looks interesting too, but too bloated for what I want.
