I am connected to a router by wifi or lan. But every few moments (sometimes seconds, sometimes half an hour) my connection to the internet breaks down. So in one moment I can surf with my firefox and have ping times of 20 ms (wifi) to the google server. And in the next moment I can't open any pages in any browser and the ping shows no new messages first and then "Destination Host Unreachable".

This is especially odd as another computer or my smart phone stays connected at the same time to the same network and seems to notice nothing.

So I have a problem independend of wifi or lan drivers but with something else. Where should I look for logs that could tell me more information? I can't find some in syslog. Just if I reconnect to the router (wich works for another few moments) there are a lot of informations. But everythin is okay then.