ROUTER

     Router is a layer 3 (Devices which work on Network Layer mainly focus on routing) device. It is used for interconnecting different networks. Router works based upon the logical address (IP address) to forward data to other network sections. It uses Access Control List for filtering packets. Router won't forward broadcast from one network to another, it creates multiple broadcast domains. Routers can provide interconnection between different VLANs (Virtual LANs). Each interface of a router will be in different networks.

Internal Components of s Router

   1. RSP : Route Switch Processor. It is the CPU inside the Router.

  2. RAM : Random Access Memory. It is a temporary storage media. Its volatile. Router RAM includes the following :

• Running configuration : The list of configurations which are presently used by the router.
• Routing table : It is the list of all the network and path information known to the router.
• CDP (CISCO Discovery Protocol) table : Protocol used only by CISCO devices. CDP used for collecting information about neighboring CISCO devices and stored in CDP table.
• ARP (Address Resolution Protocol) table : To find the MAC address and stored in ARP table.

  3. ROM (Read Only Memory) : Used for storing frequently used data. Its non-volatile. Router ROM includes the following :

Like

• POST (Power ON Self Test) : It is the program used by the router at power on time to check whether all the basic internal components and connectors are present and are working properly.
• Boot Start Loader : It is a program to load the operating system.
• Mini IOS (Inter-networking OS) : It is the miniature version (boot-able portion) of the operating system. It is not fully functional.
• ROM monitor mode : It is an accessing mode of router, normally used for troubleshooting purpose.

  4. NV RAM (Non-Volatile RAM):Router stores the start up configuration and the configuration register values (determine and control the routing process of the router). These values are in hexadecimal form.

   5. Flash Memory : It is the place where router store the fully functional IOS in compressed form.

Connectors of a Router ....click here

1. Console port : Used for connecting a computer directly to a router for managing. Connector: RJ 45.
2. Aux port (Auxiliary port) : To connect the router from remote location using an analog modem. Connector: RJ 45.
3. AUI port (Attachment Unit Interface) : It is used to connect to a LAN using coaxial cable. Connector: DB 15.
4. Ethernet/Fast Ethernet : For  LAN connection, using twisted pair cable. Connector : RJ 45
5. Serial/Smart serial : Connection to WAN or to another router. Connector : DB 60.
6. BRI (Basic Rate Interface) : Used to connect ISDN (Integrated Service Digital Network) to WAN. Connector : RJ 45.