Router as a computer

Router as a computer

The basic purpose of a router is to route in and out from the source of information to its destination with specific addresses. Route works as computers that focus and specific in sending packets of data over the data network across the globe. Route have a special task and responsible for the purpose of interconnecting among networks by choosing the best path or route for a packet data to travel and forwarding packet data to their destination. Router is just like a postmaster of the network, where all needed information is available to the journey of the packet data from its source to its destination.

Routers works as the network center where all related information must pass through a specific route to ensure all packets data will be forwarded for its source to its destination correctly. In general routers have 2 obvious connections:

• WAN connection (involve public ISP)
• LAN connection


The main purpose of this router in the network is to ensure and examine the entire data packet’s passes through its and verify all of the data packets destination IP address, and finally determines the finest path by obtain the assist of a routing table. This mean that the final route will be determines by the most reliable route of the routing table.

Inside the router

Component Function
1 CPU Executes operating system instructions
2 Read-only memory (ROM) Holds diagnostic software used when router is powered up. Stores the router’s bootstrap program.
3 Non-volatile RAM (NVRAM) Stores startup configuration. This may include IP addresses (Routing protocol, Hostname of router)

4 Flash memory Contains the operating system (Cisco IOS)

5 Interfaces There exist multiple physical interfaces that are used to connect network.
6 Random access memory (RAM) Contains the running copy of configuration file. Stores routing table. RAM contents lost when power is off

Summary

 Routers are computers that specialize in sending data over a network.
 Routers are composed of:
-Hardware i.e. CPU, Memory, System bus, Interfaces
-Software used to direct the routing process
 IOS
 Configuration file
 Routers need to be configured. Basic configuration consists of:
-Router name
-Router banner
-Password(s)
-Interface configurations i.e. IP address and subnet mask
 Routing tables contain the following information
-Directly connected networks
-Remotely connected networks
-Network addresses and subnet masks
-IP address of next hop address

 Routers determine a packets path to its destination by doing the following
 Receiving an encapsulated frame & examining destination MAC address.
 If the MAC address matches then Frame is de-encapsulated so that router can examine the destination IP address.
 If destination IP address is in routing table or there is a static route then Router determines next hop IP address. Router will re-encapsulate packet with appropriate layer 2 frame and send it out to next destination.
 Process continues until packet reaches destination.
 Note - only the MAC addresses will change the source and destination IP addresses do not change.



Source : CISCO , CCNA2 Router and Routing Basic