overview <ul><li>A device which forwards packets between networks </li></ul><ul><li>The forwarding information is based on network layer information , routing tables </li></ul><ul><li>It works at layer 3,NETWORK layer </li></ul><ul><li>Can connect different networks segment ,if they are in same building or even on the opposite side of globe </li></ul><ul><li>Work in LAN,WAN environments </li></ul><ul><li>Two primary functions:- </li></ul><ul><li>1.) Determines the best path </li></ul><ul><li>2.) Shares details of routers with other routers </li></ul>
Two basic types:- Fixed configuration: Routers whose interfaces are installed during manufacturing and can not be changed by the user e.g. 800s and 2500s. Modular: Routers with “slots” that can accept a number of interface adapters. A wide variety of interfaces are available including Ethernet , Synchronous serial, Asynchronous serial. Modular routers usually have some fixed interfaces as well.
Front view of router: Rear view of router: Flash module Fast Ethernet ports 0/0 and 0/1 USB port High-speed WAN interface card slots Auxiliary port Power cable connector Console port
<ul><li>Internetwork operating system:-- </li></ul><ul><li>operating system of router is known as IOS. </li></ul><ul><li>IOS is a multitasking operating system that is integrated with routing, switching, internetworking, and telecommunications functions. </li></ul><ul><li>The whole of IOS of router is contained in a file known as IOS image file. </li></ul><ul><li>Different routers can have same or different IOS , mainly depends upon the features that are included in IOS. </li></ul><ul><li>Routers has its own user interface. Some of routers works in GUI but CLI is much more common for configuring routers. </li></ul><ul><li>Some routers also have ability to run IPV6 or have ability to perform NAT[network address translation] like features. </li></ul>
Working of router:- Routing method:- 1.)directly connected network 2)Static routing 3.)dynamic routing I have next hop address.
Directly connected network:- A directly connected network is a network that is directly attached to one of the router interfaces. When a router interface is configured with an IP address and subnet mask, the interface becomes a host on that attached network. Static routing:- In static routing, we provides the path to routers ,i.e. the paths which are fixed in the routing table that are followed by routers without caring weather the path is long or short. Dynamic routing:- In this, routers automatically learned about the different networks through dynamic routing protocols. Dynamic routing protocols are used by routers to share information about the reach ability and status of networks. Dynamic routing protocols perform several activities, including: 1.)Network discovery 2.)Updating and maintaining routing tables
Interfaces:- LAN interfaces : like Ethernet ports WAN interfaces : serial ports comes in this category. Auxiliary and console ports are known as management ports Dynamic routing protocols:- RIP (Routing Information Protocol) IGRP (Interior Gateway Routing Protocol) EIGRP (Enhanced Interior Gateway Routing Protocol) OSPF (Open Shortest Path First) IS-IS (Intermediate System-to-Intermediate System) BGP (Border Gateway Protocol)
Routing table principles:- These principles are from Alex Zinin's book, Cisco IP Routing. 1. Every router makes its decision alone, based on the information it has in its own routing table. 2. The fact that one router has certain information in its routing table does not mean that other routers have the same information. 3. Routing information about a path from one network to another does not provide routing information about the reverse, or return, path.
1.) A switch sorts and distributes the network packets sent between the devices on a local area network (LAN), while a router is a gateway that connects two or more networks, which can be any combination of LANs or WANs. 2.)Switch hardware oriented, i.e. it uses a special chip called ASIC(application specific integrated circuit) while Router Software oriented. 3.)switch is L2 devices, because packet transferred through MAC address while router is L3 devices , because packet transferred through IP address. 4.) Switch works in the same network while Router connected between different network. Difference between switch and router:-