I've got a Linksys WRT160NL hooked through a cable modem provided by ISP. My connection speed (as advertised from my ISP) is 7mb download and 1mb upload. For about a month straight I was getting .1mb download and upload, which is when I called my ISP to flip out about how crummy their service was. Customer Service had me plug direct to the modem (duh) and I was getting 5mb download and 1 mb upload. So obviously the router. I did a factory reset on my router the following week, and everything went back to normal, I was getting my full 7mb download and 1mb upload. However about a week has passed, and now I'm down to .5mb download and .2mb upload. When I am running speed tests I am the only computer using the internet at the time of the test. My router is somehow bottlenecking my connection speed, but I don't understand how. I have 3 computers and 1 printer connected through LAN, and currently am not utilizing the wireless feature (except for visitors). The wireless is password protected however, so I am pretty sure it isn't hijackers. Let me know if you guys think it is a faulty router, or there is some sort of cache that is filling up...I don't really know. Let me know, I appreciate it.
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are you using the latest Firmware for your router?
I had attempted to do an update at one point and it said the update failed. I'll try running another firmware update. It worked for at least a year with no issue until about 1 or 2 months ago it started acting up like this. I'll take a stab at updating the firmware again. I'll let you know how it goes.
When you are getting these drops in speed, try plugging into the modem and see if you are getting the same speeds because it could be that the isp is acting up. I know you said that it wasn't before, but it is simple trouble shooting.
After that, simple reboot the router and see if the speed increases.
Also, check the logs in the router and see if clearing it does anything.