Alabalcho, thanks so much for fast response! I do know my SB6121 is only a modem, not a router. I normally have modem connected to router (with WPA security) & then router connected to laptop thru ethernet cable. But right now, having modem directly connected to laptop is only way I can get on internet. I have Kaspersky security on laptop with strong firewall. If router is connected in home network, I can't access internet. I do not have desktop anymore it had XP on it, so stopped using due to no support or security updates. Laptop running Windows 7 is only computer now in home network.
Maybe some background info will help you, help me. My problem started after thunderstorm a few days ago. A few hours after storm passed, I tried to check email & couldn't get on line. Firefox would not work at all. Tried IE & it connected, but would only reliably connect to home page after swirling for awhile. If I clicked a link from home page, or tried to open a 2nd tab for another website, it would give me "page not available", or simply do nothing. I rebooted computer, problem still there. Then husband said his tablet couldn't get online; it kept showing message it was "finding IP address", but without success. Same thing with smart phone. We tried several times, & usually tablet did not connect, but 1 out of maybe 10 time it would connect, but only for a few seconds, then disconnected. I rebooted everything - trying to reset whatever was not working. I disconnected and re-connected computer, modem & router several times,& in different orders of re-connecting, but nothing reset the network. I took almost a whole day "troubleshooting" all of the network components with support people, trying to find out if it was a problem with my ISP, the modem, the router, or the computer. Diagnostics on computer indicated internal adapters were working, but I had no internet access. Support people with the ISP, the modem mfg & the router mfg. - all said problem was caused by 1 of the other components (big surprise there, huh?).
My ISP said weak signal on modem, & since I owned the modem, not them, I needed to fix or replace it. Modem mfg. support person helped me most - after about 45 min. of connects/re-connects, pings, etc., then repeating those steps in different order, all to no avail, we finally got lucky & was able to get online briefly to Arris website just long enough to do factory reset on modem. Rebooted modem & computer again & modem started working - but only if connected directly to computer. The minute I hooked up router again I could not get internet access.
Then called Linksys to troubleshoot router. Went thru the connect/disconnect power, same with cable connections from modem to router & computer, also tried plugging Ethernet cable into different ports on router (had 4 ports), but nothing worked. Support person & I even went thru steps to set up new network, but that didn't work either, so she said I needed a new router.
Worth mentioning is a weird thing that happened during all this - after connecting & disconnecting ethernet cable many times during trouble shooting sessions, I noticed the port light on router display area (that showed which port the ethernet cable was plugged into) stayed ON in port #2 even though cable had been taken out of that port! If I plugged ethernet cable into another port of router, both port # lights came on & blinked. I was occasionally able to briefly connect to internet (probably due to fewer users on ISP lines since it was 2 AM at this point), but connection was weak & would not open more than 1 tab, etc. & would then disconnect again. Finally gave up on router & totally disconnected it from network. I plugged modem directly into computer again & have had no problems connecting to internet. Thus, my conclusion that I need a new router. Do you concur?
Linksys support person tried a fairly hard sell to get me to buy a new EA6500 router at "special price" while I was on phone with them. I declined offer until I could do research. Research found there are now AC routers as well as N routers to choose from, & then I got into compatiblity research about which type would work with my laptop...and here I am. I'm trying to figure which router to buy that is compatible with laptop & that I can afford.