Operating Cisco Routers

Routers differ from switches in terms of their core purposes. Switches forward Ethernet frames by comparing the frame’s destination MAC address to the switch’s MAC address table, whereas routers forward packets by comparing the destination IP address to the router’s IP routing table. Ethernet switches today typically have only one or more types of Ethernet interfaces, whereas routers have Ethernet interfaces, serial WAN interfaces, and other interfaces with which to connect via cable and digital subscriber line (DSL) to the Internet. Routers understand how to forward data to devices connected to these different types of interfaces, whereas Ethernet switches focus solely on forwarding Ethernet frames to Ethernet devices. So, while both switches and routers forward data, the details of what can be forwarded, and to what devices, differ significantly.