IS-IS Protocol

IS-IS stands for the Intermediate system - Intermediate system and that protocol is the oldest protocol. Intermediate system - Intermediate system protocol was developed by the Digital Equipment Corporation Network just for the connectionless mode network service. In the past time for all the service provider’s CLNS routing Intermediate system - Intermediate system protocol developed by the DECNET. ISIS is the oldest protocol and that protocol is the protocol of that time when IP was not the protocol at that time. International organization for standardization created something like to UDP and IP are called the CLNP and CLNS. Basically, the simple terminology of intermediate system is router. Intermediate system to intermediate system is the protocol that is not developed for the IP it was developed for the CLNS and later it was also developed for the IP and after that ISIS known as the Dual IS-IS.

Following are the capabilities of Intermediate system to Intermediate system:

Intermediate system to intermediate system is the Interior Gateway Protocol.

That protocol is the protocol which is similar like Open shortest Path First.

That protocol is the protocol which forms the peer adjacencies

Intermediate system - Intermediate system that is the link state routing protocol.

This protocol has the areas.

This protocol similar to OSPF and exchange the link state packets like OSPF.

This protocol builds the link state database.

The algorithm of the IS-IS is Dijkstra algorithm that is also known as the shortest path first algorithm.

The administrative value of the Intermediate system to intermediate system in Cisco is 115 and the preference in Huawei is 15.

Distance Vector Protocols

These protocols are the protocols that are used to determine the best path for the packets on the basis of the distance and these protocols are the protocols that measure the distance by the numbers of the layer 3 device that is router. In distance vector protocols only complete routing table will be transmitted and this process will consume the large bandwidth factor. In most cases if the bandwidth of the link is low than on that link there is a chance to occur congestion.

Link Sate Protocols

Open Shortest Path First Protocol

Open Shortest Path First is the dynamic routing protocol and this is layer three means network layer protocol. This protocol is the most using protocol in the industry. And this protocol is the protocol that is also known as the link state protocol. The word link means interface of router and the word state is "description of interface and it's connected to neighbor router".

Major Points

Open Shortest Path First is the link state protocol.

OSPF is the Interior gateway protocol that configure with in the single autonomous system.

OSPF Administrative Distance value is 110 in cisco devices and it is the configurable parameter. Basically AD value describe the priority of routing information.

OSPF based on the Dijkstra's Algorithm and this algorithm is also known as the shortest path first algorithm and the other third one name is link state algorithm.

There are the following three tables that exist in this protocol 1)Neighbor table 2)Database table that is also known as the topology table 3)Routing Table and in this table only best paths are  exists.

Metric/Cost: when cost is less than it will be preferred path according to the Shortest Path Algorithm. Means if the bandwidth is greater than that path will be preferred because OSPF's cost is bandwidth.                                 [Cost ∝ 1/Bandwidth]

Area (logical Area) basically it is the collection of routers. So there are the two types of area:

1)Single Area: In this area type only single area exist that consist of the multiples routers.

2)Multi Area: In multi area there are the multiples areas in which area 0 is the backbone area       and the other areas are the non backbone area. All the none backbone area should have to               directly connected to the backbone area means with area 0.

LSA means link state advertisement and in OSPF LSA is the source of the exchanging information.

Pieces of concept

Before this configuring protocol on the devices we should have to know that these three important piece of concept that are very important:

Process ID : Process ID is the id that is the identification of the OSPF that is 2^16 which is equal to the 65535 and the range we can set is 1-65535. This is the compulsory parameter which is very important.

Wildcard Mask : OSPF support the wildcard mask that is the inverse of the subnet mask.