I'm running Kubuntu 12.10, upgraded from 12.04. After the upgrade I discovered that although I can access my local network without any trouble, I can't access any remote locations -- not even by IP number. So the difficulty probably has to to with routing or some related issue. Since I do no better with IP numbers than with URLs, it's almost certainly not nameserver-related. And since local access works correctly, it's not a low-level problem such as something wrong with Network Manager. Since I still can access the Net using Windows on the same machine, it's not anything with my router or beyond, either.

I have another laptop sitting next to this one, also running Kubuntu 12.10. On the other laptop, everything works, so I can make comparisons. On the working laptop, the output of netstat -a starts with a number of tcp lines; on the troublesome one, those lines are not to be seen.

I'm not expecting a solution from here, but at least I'd like to know what kinds of things I should be investigating and where I can learn how the routing mechanisms work.

I assume you've tried ping to reach the remote systems.

A useful command would be traceroute. It can tell you where the connection is failing and help you narrow your search.

Here's a good article on traceroute. http://www.thegeekstuff.com/2012/05/...oute-examples/

See also man traceroute.

I tried ping 8.8.8.8 (easy to remember) which pings Google. I get "connect: Network is unreachable". And traceroute just comes up with rows of asterisks.

I wish I knew just what goes on behind the scenes with that ping command. Just what is the networking software doing in order to try to locate the network? There's lots of documentation on networking, but I can't find any that addresses that question. It's probably there somewhere but lost in the clutter.

Here's a rather detailed article on troubleshooting network connections.

http://www.linuxhomenetworking.com/w...roubleshooting

If the problem machine is wireless, I would suggest starting by connecting it to the router or hub with a known-good cable and retesting as a first step. That will help determine if it's a general problem or a wireless problem.

If you come back with more questions, please post the output of these commands from a terminal.