Most broadband routers are a combination Ethernet switch or hub and Network Address Translator. They usually include a Dynamic Host Configuration Protocol (DHCP) server, Domain Name Service (DNS) proxy server, and a hardware firewall to protect the Local Area Network (LAN) from malicious intrusion from the Internet. Some people also opt for a software firewall as well such as Zone Alarm or the built in firewall of Windows XP.

All routers have a Wide Area Network (WAN) Port. This port connects to the to a DSL or cable MODEM for broadband service. Many recent broadband routers are combination routers/Ethernet switch (or hub) that have multiple Ethernet ports to connect more than one PC. This form s a LAN. These ports allow the PCs to share the WAN port and broadband Internet connection and perform LAN functions, such as Windows file and printer sharing. 

Some routers have a single WAN port and a single LAN port and are designed to connect to an existing LAN hub or switch to a WAN. Ethernet switches and hubs can be connected to a router with multiple PC ports to expand a LAN. Depending on the capabilities of the router and the switches or hubs, the connection between the router and switches or hubs may require straight-thru or crossover networking cables.

Besides the inherent protection features provided by the NAT, many routers have a built-in, hardware-based firewall. Firewall capabilities can range from the very basic to quite sophisticated. Among the capabilities found on leading routers are those that permit configuring TCP/UDP ports.  Some routers have ports for USB connections to computers on a LAN and some have wireless LAN capabilities.

In short, a hub glues together an Ethernet network segment, a switch can connect multiple Ethernet segments, and a router can do those functions plus route TCP/IP packets between multiple PCs on LAN and a WAN, or even more.

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[tags]Ethernet, hub, switch, router, broadband, LAN, WAN, wireless, ports, NAT, [/tags]