A linksys router is a Network Address Translation Device (NAT). It is not a True Firewall, but it has some properties of a firewall.
1)it provides a non-internet accessible internal network. In other words if you dont have a NAT device, and you are plugged in directly to the DSL or Cable Modem, your computer is accessble to anyone on the internet.
2) The Linksys NAT device acts as a “Firewall” in the sense that it hides you on a private network. The only thing that is accessible to the internet is the Linksys. It also has features that allow you to foward requests of your choosing to pass through. IE POLLING uses port 20000, unless you open these ports the request is denied giving you protection. Common programs we will setup to pass through is PCA, VNC polling.
3) it is also a Switch as well and acts as a DHCP server. Dynamic Host Configuration Protocal. the router will set up all the appropriate TCP/IP settings to get on the internet.
4) It also allows all machines on the network to share 1 safe internet connection.