ISIS Packet Type:- CSNP

CSNP:-

This is used to maintain consistency in a link state database

These are sent every 10 seconds in a point to point network

If a router receives outdated CSNP it sends the updated LSP

In a broadcast network these are sent by the DIS

CSNP contains the following information:-

Remaining lifetime of the LSP in seconds

LSP ID

LSP checksum

LSP sequence number

If a device receives a CSNP it checks its database if it finds missing information it requests information with the help of PSNP

Packet Length is the size of the CSNP in bytes

Source ID:- This is the system address of the router which originated the packet.

Start LSP ID:- LSP id of the starting LSP

End LSP ID:- LSP ID of the last LSP

Given above is the TLV fields for  CSNP.

Packet capture for  CSNP:-