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What is routing protocol ?

January 26, 2010

What is routing protocol ?

Well start with the routing Protocol, Routing Protocol is the dynamic way to route the traffic or you can say the route the packets in the WAN domain. It can be done by Static routing but we are using routing dynamic protocol in many of the cases. Now question raised, if we have the Static routing and we can use static routing for route the packets then why we are using the Routing protocols in some the cases.

The Reason why we are using the Routing Protocols is there are hundreds or thousands of subnets routing from one device to another device and if you are using the Static route you have to use the static route for every subnet in a manual way and it takes time and also create a lot of confusion or difficult to manage as well. To resolve this problem Routing Protocol comes in to the picture which understand the subnets routing in an algorithm and routed to the connected routers via a path and the rules are set by the routing protocols. Some time people says that it is called as the dynamic rules of the protocol to route the number of the subnets from one device to another.

So we have number of the routing protocols used and these routing Protocols are as below:
  • RIP : Routing Information Protocol - AD 120
  • IGRP : Interior Gateway Routing Protocol - AD-100
  • EIGRP : Enhanced IGRP AD-90
  • OSPF : Open Shortest Path First AD-110
  • IS-IS : Intermediate system to intermediate system AD-115
  • BGP: Border Gateway Protocol AD-20
Types of Routing Protocols
Fig 1.1 -Types of Routing Protocols

There are two category of the interior routing protocol and they are 
  • Distance Vector Routing Protocol
  • Link State Routing Protocol
Distance Vector Routing Protocol depends upon the distance between the source and the destination. It always prefer the route where distance between the source and the destination is low or sometimes people say lower hop count. The routing protocol under distance vector is as :
  • RIP
  • IGRP
Link State routing protocol is the protocol which works on the algorithm, like wise OSPF routing protocol works on the Dijkstra algorithm which depends upon the parameters like cost, Better the cost, the path will be selected. The routing protocol comes under Link state rules are 
  • OSPF 
  • IS-IS
EIGRP is a mixed protocol and can have the features of Distance vector as well as the link state. it also works on the parameters and will be discussed in the later stage when we will explain the full operation of the protocol.

There is another category of the routing protocol and called as external protocols. All the above routing protocols described yet are internal protocols.

BGP - Border gateway routing protocol is only one external routing protocol and also called as path vector routing protocol which is used to connect between two different AS- Autonomous systems or you can say ISP's. We will discuss the BGP in detail in further post.

We will come up with all these protocols one by one in details and will also show the use cases and the labs around all these routing protocols.

Please let me know if there is any questions around the basic concepts of the routing protocols