IS-IS Protocol

Fig 1: 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.
• IS-IS is the purely layer 2 protocol because of the one reason it is on top of the ethernet header and that protocol is the protocol that is not encapsulate in the IP packet as compared to the Open shortest Path First and Enhanced Interior Gateway Protocol.