Additional hardware requirements to add more than 4 computers onto the Linksys 4 port router :

The Linksys Dhcp server (router) can handle up to 253 Dhcp clients.  In order to physically connect more than 4 computers to the Linksys you need an Ethernet hub (or switch).  Hubs/switches come in 4 port, 8 port, 16 port, and 32 port configurations.  Hubs/switches can be connected together to allow you to connect as many computers as needed.  Hubs typically cost about $5 per port.