From the Manufacturer
The Linksys EtherFast Cable/DSL Voice Router is the perfect solution for connecting a small group of PCs to a high-speed broadband Internet connection or a 10/100 Ethernet backbone--and it features Voice over IP telephone calls powered by Net2Phone. With the EtherFast Cable/DSL Voice Router installed, no other special hardware is necessary for telephone calls. An ordinary telephone connects to the RJ-11 port (telephone jack) on the back of the EtherFast Cable/DSL Voice Router, and calls are routed by Net2Phone's superior quality network to anywhere in the world--significantly reducing long distance charges.
Configurable as a DHCP server for your existing network, the EtherFast Cable/DSL Voice Router acts as the only externally recognized Internet gateway on your LAN. The EtherFast Cable/DSL Voice Router can be configured to filter internal users' access to the Internet and serve as an Internet firewall against unwanted outside intruders. Not only does it make Internet access available for up to 253 PCs on the network, it also adds an additional voice phone line for outgoing calls at no extra cost. None of your PCs even have to be turned on to make calls. The EtherFast Cable/DSL Voice Router handles all of your network and telephony needs in one integrated unit.