Summary
IS-IS is a link-state protocol based on the OSI Intradomain Routing Protocol, and is designed for use with the ISO protocol. It can support pure IP environments, pure OSI environments, and multiprotocol environments. There are four packet types in IS-IS: hello, LSPs, CSNP data units, and PSNP data units.
Link-state protocols (LSPs) are based on neighbor relationships. Every router advertises the cost and state of its links. There are four LSP processes: receive, update, decision, and forwarding. LSPs are flooded to provide the routers a consistent view of the network. Flooding and synchronization are performed via CSNP, PSNP, SSN, and SRM bits.
There are two levels of hierarchy in IS-IS. In level 1, routers have full knowledge of all ...
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