Routing

Routing is a process performed by the router to forward data packets are passed to the destination network from origin to destination address. A router that works on OSI layer 3 forwarding decisions based on destination IP address of a packet. To take the right decision, the router must learn a way to reach to the network that are not directly connected with it (the remote network). The first way is when a network administrator to write a routing table into the router configuration, a list of networks that can be achieved by the router in question. This technique is called with Static Routing, in the sense of each route should be added or removed from the routing table manually in order to reflect the actual network topology. In a large network, this kind of manual activity will take more time and less practical, requiring a more flexible way.
A router can recognize each interface attached to it, in other words, he also recognizes that every network connected directly to it by IP address on each interface is attached. If he collects the facts of this and put it in a Routing Table, then he sends this list to any other router that connected directly with him, and vice versa, he received a list of other router's routing table through the same process, then there was a process of Dynamic Routing .
The process of exchanging routing table is held in:
1) automatically, without the involvement of a network administrator to write a routing table, and
2) dynamic, meaning that every change in topology that occur will be distributed by the router is concerned, so that routing tables will be in a condition that is always up to date. Furthermore, each router's routing table to process the list he received from another router and forwarding decisions based on parameters that are more complex concerning the size of the network segment, the amount of bandwidth available from a link, and protocol-run. This will have significant influence if a router finds there is more than one route to reach to a segment of the same network.