Networks allow people to communicate, collaborate, and interact in many ways. Networks are used to access web pages, talk using IP telephones, participate in video conferences, compete in interactive gaming, shop using the Internet, complete online coursework, and more.
Ethernet switches function at the data link layer, Layer 2, and are used to forward Ethernet frames between devices within the same network. However, when the source IP and destination IP addresses are on different networks, the Ethernet frame must be sent to a router.
A router connects one network to another network. The router is responsible for the delivery of packets across different networks. The destination of the IP packet might be a web server in another country or an email server on the LAN.
The router uses its routing table to determine the best path to use to forward a packet. It is the responsibility of the routers to deliver those packets in a timely manner. The effectiveness of internetwork communications depends, to a large degree, on the ability of routers to forward packets in the most efficient way possible.
When a host sends a packet to a device on a different IP network, the packet is forwarded to the default gateway because a host device cannot communicate directly with devices outside of the local network. The default gateway is the intermediary device that routes traffic from the local network to devices on remote networks. It is often used to connect a local network to the Internet.
This chapter will answer the question, “What does a router do with a packet received from one network and destined for another network?” Details of the routing table will be examined, including connected, static, and dynamic routes.
Because the router can route packets between networks, devices on different networks can communicate. This chapter introduces the router, its role in networks, its main hardware and software components, and the routing process. Exercises that demonstrate how to access the router, configure basic router settings, and verify settings are provided.