just connected two routers so we could have wireless in the back of our apartment; it’s an old apartment and the walls must be gnarly because we barely get a signal.
http://www.tweaktown.com/articles/1575/using_an_old_router_as_a_diy_wireless_access_point/index.html
but had some issues adjusting the new router settings; these are instructions for next time in case i forget.
fyi i used a linksys wrt54g router for the additional router, and a linksysN router for the main router.
main router should be set up.
- while plugged in to main router, go on to the wireless router admin page (common default is here: http://192.168.1.1/ admin admin)
- check ip address, write it down. also note the range and starting # of the DHCP server settings
go to the new additional router, plug into it, go on to the wireless router admin page:
- under setup, disable DHCP server. give this router a unique ip address - outside of the range on the main router’s DHCP range, and the last number should not be above like 250 or something. Basically just set the i.p. for the additional router to something different than the main router – i.e. if your main router is 192.168.1.1, and its DHCP range is 192.168.1.100-192.168.1.149, then 192.168.1.2 or 192.168.1.3 or whatever will work. save.
- retype this new unique ip address in the url, as the current url will stop working as we’ve changed it.
- under administration tab, disable UPnP. save.
- under security, disable SPI Firewall Protection and uncheck all boxes. save
- under wireless, set up a username/pw. save.
this sets up the router.
IMPORTANT: plug LAN to LAN, don’t use the WAN port which seems logical…it does not work.
Then on each (PC)device you plan to connect, do the following:
- connect to the new network w/pw.
- open the network > view status > properties > IPv4
- type in another unique ip address
- subnet should stay the same as the orig router’s subnet.
- default gateway and preferred DNS server should be the main router’s ip address.
do this for each computer. (Macs and iPhones just work themselves out automatically 
)