Can some one suggest a software for a small home network to monitor the amount uploaded / download from the internet but not the local traffic on the LAN. I know there are similar questions like these
How can you monitor internet data usage?
Monitoring inbound and outbound internet traffic
but the suggested softwares in these questions like vnstat dont consider if the traffic is for local network or internet which means that I can not know if I am reaching my ISPs monthly cap on bandwidth. I have googled for this and found only one software i.e ipac-ng but it is not straight forward. I need something that I a normal user can use easily i.e without changing iptables rules or adding routes.
"Do You Have Limited Internet Plan? Use NTM (Network Traffic Monitor)!" - http://www.webupd8.org/2010/12/do-you-have-limited-internet-plan-use.html
I would check out conky (just go into the Ubuntu Software Center and type it in).
Then find some guides on how to use it, but it provides a wealth of options to monitor virtually every aspect of your computers performance. I do not use it regularly myself, but the options are extensive.
The firewall program 'firestarter' (again, in the software center) also monitors upload/download usage but only from when you turn it on each session.
Hope they point you in the right direction!