Description of Router

v  Router is an intelligent network device.

v  Routers are combination of hardware and software and used to connect separate networks to form an internetwork. Router can be used like bridges to connect multiple network segments and filter traffic. Also, unlike bridges, routers can be used to connect two or more independent networks.

v  For example a FDDI networks and an Ethernet network can interconnected so that users on each network can share resources on the other network and still both network continue to function separately.

v  A router is a device that extracts the destination of a packet it receives, selects the best path to that destination, and forwards data packets to the next device along this path. They connect networks together; a LAN to a WANfor example, to access the Internet. Some units, like the Cisco 1800 (pictured), are available in both wired and wireless models.

v  A more precise definition of a router is a computer networking device that interconnects separate logical subnets.

v  Routers are now available in many types, though all are fundamentally doing the same job.

v  Use dynamic routing

v  Operate at the network layer

v  Remote administration and configuration via SNMP

v  Support complex networks

v  The more filtering done, the lower the performance

v  Provides security

v  Segment networks logically

v  Broadcast storms can be isolated

v  Often provide bridge functions also

v  More complex routing protocols used [RIP, IGRP, OSPF]

v  If router uses static routing, the routing table must be updated manually by the administrator. Each individual route must be added by manually. The router will always use the same path to a destination, even if it is not necessarily the shortest or most efficient route.

v  Dynamic routers communicate with each other and are constantly receiving and are constantly receiving updated routing tables from other routers. If multiple routes are available to a particular network, the router will decide which route is best and enter that route into its routing table.

v  Can connect networks of different physical media and network architectures Can choose the best path for a packet through an internetwork reduces network traffic by not forwarding corrupt packets

v  More expensive a more complex than bridges or repeaters. Slower than bridge because they perform more complex calculations on the packet Only work with routable protocols (TCP/IP, IPX/SPX, DECnet, OSI, XNS).