have a small Ethernet network based around a hardware router. Can I use a second router to expand the network?
You certainly don’t need a router to connect more computers to your network–just a switch or hub uplinked into one of the router’s ports will do. But if you have an old router with built-in switch lying around, all you need to do is shut off its built-in DHCP server and set its IP address so that it’s in the same Class C range as the addresses being served by the main router, but outside its DHCP server range. For example, if your main router has an address of 192.168.1.1 and its DHCP server is set to lease addresses from 192.168.1.10 to 192.168.1.50, set the “retired” router to 192.168.1.254. Make sure you use only the “retired” router’s LAN ports for connecting your additional computers. You’ll also need to use one of the “retired” router’s LAN ports to connect to one of your main router’s ports. Use a crossover cable to do this unless one of the routers has uplink capability. If the “retired” router has a built-in print server, you can still use it, too. You’ll be able to reach it
