Posted 21 December 2009 - 01:09 PM
Depending on who your internet is with, most places have a line coming in to your home that leads to a modem. The modem has a CAT5 cable coming out to (in your setup) the router's WAN port.
If you have a modem, check to see if it is rebooting as well when the internet disconnects. If so, I would contact your ISP for assitance.
If it is just your router, there are a couple things you could try, but ultimately it sounds like a router replacment would be the way to go.
I would recommend reseting the router back to the factory defaults to clear any misconfigured settings via the reset button. Before doing so, record any ISP specific information. Such as if you are using a PPPoE connection, you will need the Username and Password information. Refer to the manual for reconfiguring the router.
I know with the Linksys BEFW11S4 you need to do a firmware update for the issue you have described. If you call D-Link, it is likely they will give you the same answer. Refer to the manual if unsure on firmware updates. If done incorrectly, your router will become a paperweight.
90% of the time, when I see this issue it is a failing router. Something to consider before investing too much time in troubleshooting it.