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When you're studying to pass the BSCI exam and earn your CCNP certification, you're going to be introduced to ISIS. ISIS and OSPF are both link-state protocols, but ISIS functions fairly differently from OSPF. You must master these particulars in order to earn your CCNP. One of the significant differences in between OSPF and ISIS will be evident to you when you very first begin your BSCI exam studies, and that is the terminology. ISIS utilizes terms that no other protocol you have studied to date makes use of, and studying these new terms is the first step to BSCI and CCNP exam good results. tyent uce-9000t go First off, what does "IS" stand for in "ISIS"? It stands for "Intermediate Technique", which sounds like a group of routers. As opposed to Autonomous Systems, which are logical groups of routers, an Intermediate System is merely a single router. That is it. tyent uce-9000t You are going to also turn out to be familiar with End Systems, referred to in ISIS as an "ES". The End Method is merely an end host. ISIS and OSPF each use the notion of areas, but ISIS takes a different strategy to this idea. ISIS routers use three diverse types of routing levels, according to the area a router has been placed in. Level two routers are linked only to the backbone and serve as a transit device amongst non-backbone regions. Level 1 routers are completely internal to a non-backbone region. ISIS uses both Level-1 and Level-2 Hellos, meaning that the two types of routers just mentioned can't form an adjacency. Luckily for us, there is a middle ground, and that is the Level 1-two router. These routers connect non-backbone areas to backbone places. L1-L2 routers preserve two separate routing tables, one particular for L1 routing and another for L2 routing. This is the default setting for a Cisco router, and L1-L2 routers can type adjacencies with each L1 and L2 routers. Part of the challenge of mastering ISIS is acquiring utilised to the differences between ISIS and OSPF. Keep studying the terminology, master one particular idea at a time, and soon you are going to be a master of ISIS and a CCNP to boot!