Introduction to IS-IS

Hello Mohammad.

Think about the CSNP as a packet that contains all of the LSPs from the current database. If this packet is sent to another router, the recipient will have a complete list of LSPs, in other words, it will have the sending router’s current view of the network. These packets are similar to OSPF database description packets.

The PSNP is a partial list of LSPs. This is sent as a response to a specific request for specific information (for specific prefixes). This can be used to request an LSP (or LSPs) and also to acknowledge the recipt of an LSP.

@ReneMolenaar will take your request to add more information about this subject into consideration. Thanks for the feedback!

I hope this has been helpful.