Network router is a device or a piece of software in a
computer that forwards and routes data packets along networks. A network
connects at least two networks, commonly two LANs or WANs or a LAN and
its ISP network. A router is often included as
part of a network switch. A router is located at any where one network meets another,
including each point-of-presence on the Internet. A
router has two key jobs:
- The router ensures that information doesn't go
where it's not needed. This is crucial for keeping large volumes of
data from clogging the network.
- The router makes sure that information does
make it to the intended destination.
performing these two jobs, a router joins the two networks, passing
information from one to the other and, in some cases, performing
translations of various protocols
between the two networks. It also protects the networks from one
another, preventing the traffic on one from unnecessarily spilling over
to the other. This
process is known as routing.
is a function associated with the Network layer (layer 3) in the Open
Systems Interconnection (OSI) model. Routers use network layer protocol
headers, such as IP header where the source and destination addresses
are included, and routing tables to determine the best path to forward
the packets. For the communication among routers and decide the best
route between any two hosts, routing protocols such as ICMP are used.
routers are specialized computers that send messages speeding to their
destinations along thousands of possible pathways. One of the tools a router uses to decide which path a packet
should go is a routing table.
A routing table contains a collection of information, including:
Information in the routing tables can be static
(with routes manually entered by the network administrator) or dynamic
(where routers communicate to exchange connection and route information
using various routing protocols). A routing table can be as
simple as a few lines in the smallest routers, but can grow to massive
size and complexity in the very large routers that handle the bulk of
Internet messages. As the number of networks
attached to one another grows, the routing table for handling traffic
among them grows, and the processing power of the router is increased.
- Information on which connections lead to
particular groups of addresses
- Priorities for connections to be used
- Rules for handling both routine and special
cases of traffic
Packets routed by routers to their