What is IP Routing?
IP routing is the field of routing methodologies
of Internet Protocol (IP) packets within and across IP networks. This
involves not only protocols and technologies but includes the policies of the
worldwide organization and configuration of Internet infrastructure.
In each IP network node, the following IP routing involves the determination of
a suitable path for a network packets from a source to its
destination in an IP network. Therefore the process uses static configuration
rules or dynamically obtained status information to select specific packet
forwarding methods to direct traffic to the next available intermediate
network node one hop closer to the desired final destination, a total
path potentially spanning multiple computer networks.
Networks are separated from each other by specialized hosts, called gateways
or routers with specialized software support optimized for routing.
In routers, the following packets arriving at an interface are examine for
source and destination addressing and queue to the appropriate outgoing
interface according to their destination address and a set of rules and
performance metrics. Therefore the rules are encoded in a routing
table that contains entries for all interfaces and their connected
networks. However, if no rule satisfies the requirements for a network packet,
it is forward to a default route. Routing tables are maintains either
manually by a network administrator, or updated dynamically with a routing
protocol. Routings rules may contain other parameters than source and
destination, such as limitations on available bandwidth, expected packet loss
rates, and specific technology requirements.
Routing Protocol
A routing protocol is a software mechanism by which routers communicate and
share information about the topology of the network, and the capabilities of
each routing node. It thus implements the network-global rules by which traffic
is direct within a network and across multiple networks. However, different
protocols are often uses for different topologies or different application
areas. For example, the Open Shortest Path (OSPF) protocol is
generally use for routing packets between subnetworks within an enterprise and
the Border Gateway Protocol (BGP) is use on a global scale. Therefore
BGP is the standard of worldwide Internet routing.
Types of IP Routing
The following types of IP routing are
- Static
- Default
- Dynamic
1. Static Routing
In static routing, administrator manually adds routes in each router’s
routing table.
Command
Ip route < destination network > < mask > < next hop add or
exit interface > < administrative distance > < permanent
Example: IP route 192.168.10.0 255.255.255.0
192.168.20.1
To show routing table
# show ip route
2. Default Routing
Default routing use in sub network where there is only one way.
Example: IP route 0.0.0.0 0.0.0.0 192.168.20.1
Administrative distances
Administrative distance is used to rate the trust worthiness of routing
information received on a router from a neighbour router.
Default administrative distance
The following default administrative distance are
Connected
interface
0
Static route
1
EIGRP
90
IGRP
100
OSPF
110
RIP
120
External EIGRP
170
Unknown
255 (this route will never be used)
3. Dynamic Routing
Protocols are used to find networks and update routing tables on routers.
Therefore the routing protocols used to determine the path. Example: RIP, IGRP,
OSPF, etc, and routed protocols that carries the packets, Example: IP, IPX, and
AppleTalk.
Learn about Bootstrap
Protocol (BOOTP)
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