bought a linksys router BEFW11S4 to share cable internet. I can connect internet most of time. The problem is when I use the router for a while, the light named 'WAN Link' will flash for seconds. when it flashes, the speed becomes zero. and then the light will be steady, speed becomes normal. Sometimes this problem arises frequently. The cable works well and there is no such problem when I connect cable to my computer directly, that means it is not cable's problem. Is there anyone have such situation before? and how to solve it?

It could be a result of IP SPOOFING or TCP SYN FLOODING. Check an see if your router has a security log. In the security log it should tell you if you have been attacked. Its not a malicous attack, just a denial of service attack. Its probley not, but check. I don't believe that cable uses DHCP but if it does it could be renewing its lease on that address. Or if the ISP expects to see your computer's(NIC/modem) MAC address you may need to mask the MAC address of your computer to the router. It should be a function of your router under the WAN setup. If you have connection its probley not the masking. I know it does'nt help much but look into those.

From the factory the Linksys router is set to block all LAN requests. That meens your cable service can not Ping the router to see if the IP address is still in use. Your cable company is prob sending out your IP address to another PC from the DHCP server which is causing your router to drop connection and get a new IP. Log in to your router. http://192.168.1.1 If you have not changed the default settings the User name and PW are both admin. Click on the advanced tab on the top right. Scroll down the page. You will see a spot that says Block WAN Request. Click in the dot next to Disable. Apply the changes.