An Overview of Routing and IP Address
Routing is an important function of the IP. It is the process of choosing
a path over which to send packets. The device that performs this task
is called a router. The router forwards packets from one physical network
to another. The network layer performs the routing function. A packet
or datagram carries information for routing from the originating host
to the destination host using the IP address. There are two types of routing:
Direct routing- two computers on the same physical network needing to
communicate, the packets do not require a router.
Indirect routing- two computers that are not on the same physical network
needing to communicate, the packets need a router for delivery.
Routing Process
Routing involves two key elements:
1. Host must know which router to use for destination which is determined
by the default gateway (IP address of router on local network)
2. Router must know where to send packet
There is static and dynamic routing. Static routers contain routing information
tables that are built and updated manually. Dynamic routers communicate
with other dynamic routers to calculate routes automatically using routing
protocols.
Routing Information Tables:
A routing information table is a database maintained by a router. Within
this table is contained the location of all networks in relation to the
router's location. When the packet arrives at the router, the router examines
the packet's destination network, then checks its own routing information
table. It will then determine the next router to send the packet to, and
forward the packet to that router, which is considered a hop. The following
illustration shows a simplified routing table that breaks down the basic
process.
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