In Nov 2014 my LinkSys router died. It was almost 2 years old so it was time. I went to Best Buy and bought a new LinkSys and the 2 year exchange warranty (normally I don't buy extended warranties but for routers I have learned to do so).
In July 2015 I did some research on anti-virus software and decided to buy and install BitDefender on all of my devices (6 Windows pc's and 2 Androids). About a month later I started having real issues with my network: Couldn't see some of the pc's on the network; couldn't access them; my main desktop would lose connection; etc. I figured it was the router and that it had only lasted 9 months, so I took it to Best Buy and exchanged it for a NetGear (comparable quality).
Took it home, got it up and running, and right away noticed really slow connection times and data transfer rates between pc's. After a month of frustration I took it back to Best Buy and upgraded to a LinkSys AC2600 (all of these exchanges were covered by the warranty). I took it home, got it up and running, and right away started seeing disconnects, lag times, etc. This really annoyed me. How could I get 3 dysfunctional routers within the space of 10 months?
I decided that was too improbable to believe, so after some considerable research online, and poking around, I discovered the culprit: It was BitDefender. It comes with a built in firewall (which I did not anticipate) and apparently, when it is first installed, it changes the settings on the network adapter on the pc it is installed on. In other words, it chokes the adapter with security that you would only want on a public
network, not on a home network.
The solution: Open the firewall settings, go to the "Adapters" tab, and change the "Network Type" to "Trusted" (instead of Home/Office or Public), change the "Stealth Mode" to "Remote" (had to read a bunch of FAQ's on their web site to discover that one) and set the "Generic" to "On". That last one basically tells BitDefender to not look for any specific adapter type.
After doing all of the above my home network is now working perfectly: Screaming data transfer rates, no dropped connections, immediate connections, etc. Which means most likely... Those other routers were probably fine.
Perhaps this post can help someone else avoid the frustration.