I recently moved into a new house that is 3 stories. My cable modem comes in on the first floor so my wifi router was placed down there. My home office is on the third floor so now when I am in my office at home I download the latest developerworks podcast at speeds that would rival AOL back in its dialup days. Something had to be done so what I needed was 3 linksys routers, some opensource software, and about 45 mins. Here is what I got working now....
First thing I did was take my linksys WRT54G routers and put ddwrt on them. This can be a little tricky you have to make sure and download a couple of different firmwares and put them on in the correct order and make sure you do always fun 30/30/30 restart. Always try this restart method if your router is doing something weird and a simple power restart isn't fixing it. What I recommend is going to ddwrt website looking to see if your router is supported and follow the detailed instructions to update the firmware. I ended up with 3 routers running dd-wrt.v24-13064_VINT_std.
Next I setup the main router that connects to the cable modem. This one is pretty standard configuration: WAN port on router connect to the cable modem, wireless network setup with WPA2 encryption on channel 1, and standard DHCP running. Also this router has the internal ip address of 192.168.1.1. This covers the first floor with wifi. After this I needed to setup the other two routers to be a WAP. This step took a few detailed configurations to make this happen. Here are the detailed configurations which can also be found here. I left in the Optional steps I did.
Because I don't have a network switch or a crossover cable I did do the option configuration in step 1 " This allows me to connect the WAN ports on my two WAP routers to one of the ports on the router connected to the cable modem. Also I got lucky because where my cable modem is connected on the first floor all the phone lines run to that same box and I don't have a home phone so I use the cat 5e phone lines to connect the two WAPs to the main router.
I placed one WAP on each floor. One thing I did on the WAP on the second floor was run that on channel 6 and run the one on the third floor on channel 11. Remember to set your SSID the same and your encryption the same. Now when I go from the third floor to the second floor my wireless devices change over to the wireless on that floor. The result is I rarely have less than 60% strength anywhere in my house.