How do I fix my Linksys BEFSR41 router?

Question

When I first got this router, it worked brilliantly, no problems what so ever. But when my old modem gave in, I had to get a new one. Then my router will not agree with my new modem. I cannot seem to find my installation disc that came with the router. So does anyone know how make my router work with my new modem?

Answer 1

The first thing I would recommend it to reset the Linksys router back to the factory defaults. That is generally done by pressing the reset button with a pen tip for 10 seconds.

Try connecting a desktop or laptop directly to the modem given to you by your ISP and see if you have Internet access. If you do (and you should), open up a command prompt window (Vista: http://www.petri.co.il/vista_command_pro... or XP: http://www.pcstats.com/articleview.cfm?a... ) and run the command ipconfig /all and note your IP address.

If the IP address your computer has starts with 192.168.x.x (e.g., 192.168.1.50) or 10.x.x.x (e.g., 10.0.0.50), your new modem is also acting as a router. IP addresses such as those I just listed are private IP addresses and are not routable on the Internet. Your router has taken the routable IP address that used to be passed to your router. (The old modem from your ISP was probably running in "bridge" mode and just passing through the Internet connection and IP address.)

If you instead see an address like 71.4.220.28 (anything other than 192.168.something or 10.something) on your computer, your new modem is probably already in bridge mode. Make a mental note here if you got a routable IP address or not.

Now, hook your Linksys (using the Internet or WAN port) to the modem and hook your computer to the Linksys (to one of the four LAN ports). If you had previously gotten a routable IP address on your computer, try your connection now and see if it works. Your Linksys may have been set up to do things particular to your old modem. (You can download the manual for the BEFSR41 from Linksys and follow their installation procedures at this point.)

If your computer previously had a non-routable IP address, especially if that address was 192.168.1.something, you need to change the internal LAN subnet to be 192.168.2. (or 192.168.3, .4, .5 - anything but .1. This is usually done by browsing to a configuration web site built-in to the router itself. Disconnect the router from the modem, leave your computer connected, and unplug and plug in the router. Try browsing to 192.168.1.1 to bring up the configuration page. (The default user name is blank and the password is admin. We should have reset this to these defaults when you reset the router back to the factory settings.)

On the basic setup for the router, there should be some mention of LAN IP address or local IP address. Change the settings from 192.168.1.1 to 192.168.2.1 (or 3.1 or 4.1, etc.). Click apply changes or save settings or whatever is appropriate. You will likely need to reboot your computer (or use the command ipconfig /renew in a command prompt window) to get a new IP address for your computer (on the 192.168.2 subnet). Now, try your Internet connection again.

If you're working now, great. If not, you may need to enter login information of the basic setup on the configuration screen of your router. Only your ISP can give you this info if you don't have it.

What you have done is to make the internal subnet different than the subnet of the Internet as far as the BEFSR41 is concerned. If both the WAN IP address (that the BEFSR41 got from your ISP's modem) and the LAN IP address (set by default) are on the 192.168.1 subnet, the router doesn't think it needs to do anything with the packets it sees. It doesn't route (pass them through) because they are - as far as it knows - already available on both sides of the networks it is attached to. By changing the internal one, the router will now give 192.168.2.something addresses to computers that attach to it. It will route all outbound traffic from the 192.168.2.something addresses to the 192.168.1.1 address, because that's what it's rules will now tell it. The two networks differ and the way out (and back in) is via the WAN network (the 192.168.1.1 one).

PS: I suspect the reason why you can't find your installation CD is probably because it didn't come with one. Maybe it had a CD with the manual on it, but all the setup is done though the built-in web site on the router itself.