Reader Larry Braud wrote about problems adding a wireless router to an existing wired network:
Terry, you told me a while ago that you hooked your wireless router to your regular wired router whenever you wanted wireless capability. What special do you have to do or is it just plug and play? I was trying to help my brother-in-law with his and we cannot get it to work. Wired works or wireless works, but not hooked together.
Your problem is probably DHCP servers — you can only have one running on the same subnet.
A couple diagrams in my General Networking tips section should help display the issues. They’re on my Home Network Basics 6 page, and show alternative setups for wireless (page 6 is wireless focused).
If you want to isolate the wireless network from the wired, you have to put the wireless network first (connected to the cable modem) and then connect the other router to it.
If you want to share stuff between wired and wireless, you need to put the wireless connected to the wired — AND TURN OFF its DHCP server. You will probably want to assign the wireless router a fixed IP address — such as 192.168.1.254 on a 192.168.1.x/255.255.255.0 network.
In my case, I have the wireless behind the wired router. I have turned off the DHCP server and have it set at x.x.x.254 IP address (and have the wired router NOT assigning that address — there is a range setting in the Linksys wired router’s DHCP page which controls the network IP and subnet.
Really, my wireless stays plugged in all the time, but I have it set:
1) https to get to the wireless router’s setup screens
2) wired-only can get to the wireless router’s setup (Linksys setting)