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IS-IS Protocol versus OSPF Protocol

IS-IS versus OSPF IS-IS Protocol and OSPF have some similarities and differences. Lets firstly check the similarities of these two protocol one by one: – IS-IS Protocol and OSPF are both Link-State Interior Gateway Protocols. – IS-IS Protocol and OSPF are both uses Dijkstra SPF (Shortest Path First) algorithm. – These protocols have LSDBs and […]

IS-IS Adjacency States, IS-IS Neighbourship Establishment

IS-IS Protocol Adjacency There are three types adjacency in IS-IS Protocol.These are: – Level 1 routers form L1 adjacency with L1 and L1/2 Routers – Level 2 routers form L2 adjacency with L2 and L1/2 Routers – Level 1/2 routers form L1/2 adjacency with L1/2 Routers There is no neighbourship between L1 and L2 routers. […]

IS-IS Packet Types IS-IS Protocol uses L2 encapsulation Ethernet 802.3/802.2. It do not use Ethernet II. Ethernet II is used for IP traffic. IS-IS Protocol exchanges protocol information by using Link-State PDUs (Protocol Data Units). There are four types of PDU packets in IS-IS Protocol. These IS-IS packets are : – IS-IS Hello PDU (IIH) […]

IS-IS Protocol, Address Format

IS-IS Protocol Addresses IS-IS (Intermediate System to Intermediate System) Protocol was developed as a OSI network protocol, not TCP/IP. So, normally IS-IS Protocol not uses IP address, but it uses NET (Network Entity Title) addresses. Let’s check this address issue a little. In IS-IS Protocol, NSAP (Network Service Access Point) is used as network layer […]

Basic IS-IS Topology, Level 1, Level 2, Level 1/2 Routers

Routing With IS-IS Protocol IS-IS (Intermediate System to Intermediate System Protocol is a Link-State routing protocol that is developed by ANSI ISO. It is an open standard and classless Interior Gateway Protocol (IGP). IS-IS Protocol uses Dijkstra SPF (Shortest Path First) algorithm like OSPF, to build the IS-IS Protocol databases and calculate the best path. […]


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