Recently I got a new external modem. Soon after it was installed and activated, I began experiencing issues with the internet going out for a few seconds at a time. When it comes back up, I'm still on my original page, but it is annoying, and happens often. I called my service provider, who ran tests to make sure the modem and outside line it is plugged into are working. What I need to know is what in the computer I need to check.
Try running a command like this:
pathping Google
This may take several minutes to run. Note too that if the problem is very intermittant then this may not be of help.
You are looking to see if you have any packet loss. If so, is it between your computer and your MODEM? Is the next hop from your MODEM to the next location okay with no packet loss?
If you just want to see if the connection between your local computer and your MODEM / Router is good, you just run a pathping x.x.x.x (replace x.x.x.x with the IP address of the MODEM / Router).
You can also do a ping -t x.x.x.x with that same IP address to see if you are ever timing out locally. CTRL-C will stop it.
Some other questions:
Do you have more than one computer? If so, is only one computer affected? If only one computer is affected, it's more likely an issue with that computer or its connection since others are not affected. You can also ping another machine on your local network or use the pathping to verify that the local network is reliable. Another good test is simply copying a huge amount of data between 2 machines to see if it ever hiccups.
If you can assure your ISP that everything is fine internally, then at least you have some ammunition to tell them the problem is not internal.
I'm in a similar situation - in my home, access to the internet is stone cold reliable except on hot, sunny days in mid summer. Access to the Internet dies for a couple hours every day under those conditions - likely some component out there has a problem with the heat. The ISP has sent people out at least ten times to try to find the problem, but at least I've been able to prove that the problem is outside of the house somewhere.
In addition to H's good advise above, you could also check the DNS settings.
Traditionally, the ISPs set your DNS server(s) via DHCP to their own. These DNS servers can be flaky at times, that would show up as no Internet connection in the browsers. You can change your DNS server(s) addresses to Google's and others, if that's the case...
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