Routers Essay

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Routers

A router is a type of internetworking device that passes data packets between networks based on Layer 3 addresses. A router has the ability to make intelligent decisions regarding the best path for delivery of data on the network. In this chapter, you will learn how routers use a Layer 3 addressing scheme to make forwarding decisions. In addition, you will learn how devices on local-area networks (LANs) use Address Resolution Protocol (ARP) before forwarding data to a destination. You will learn what happens when a device on one network does not know the MAC address of a device on another network. You will learn that Reverse Address Resolution Protocol (RARP) is the protocol a device uses when it does not know its own IP
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Physical, or MAC addresses, are usually assigned by the NIC manufacturer and are hard-coded into the NIC. The network administrator usually assigns IP addresses. In fact, it is not unusual for a network administrator to group devices together in the IP addressing scheme, according to their geographical location, department, or floor within a building. Because they are implemented in software, IP addresses are fairly easy to change. Finally, bridges and switches are primarily used to connect segments of a network. Routers are used to connect separate networks and to access the worldwide Internet. They do this by providing end-to-end routing. Routers connect two or more networks, each of which must have a unique network number in order for routing to be successful. The unique network number is incorporated into the IP address that is assigned to each device attached to that network. Example: A network has a unique network number - A. It has four devices attached to it. The IP addresses of the devices are A2, A3, A4, and A5. Since the interface where the router connects to a network is considered to be part of that network, the interface where the router connects to network A has an IP address of A1. Example: Another network, with a unique network number - B - has four devices attached to it. This network is also attached to the same router, but at a different interface. The IP addresses of the devices on this second network are B1, B2,

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