Which two statements about IS-IS are correct? (Choose two.)
Which two statements about IS-IS are correct? (Choose two.)
In IS-IS, Complete Sequence Number PDUs (CSNPs) are used to ensure all routers in an IS-IS network have a synchronized Link-State PDU (LSP) database. CSNPs are flooded periodically to update and synchronize the database. Additionally, CSNPs contain only descriptions of LSPs, summarizing information such as the sequence number and checksum of each LSP. Therefore, the two correct statements about IS-IS are that CSNPs are flooded periodically and that CSNPs contain only descriptions of LSPs.
AC is correct. Contained within the CSNP is a link-state PDU identifier, a lifetime, a sequence number, and a checksum for each entry in the database. Periodically, a CSNP is sent on both broadcast and point-to-point links to maintain a correct database.
LSPs contain information about the state and cost of links in the network, and are flooded periodically throughout the network. PSNPs are used to acknowledge receipt of LSPs and request retransmission of missing or corrupted LSPs. PSNPs contain only descriptions of LSPs, such as their sequence numbers and checksums. CSNPs contain a complete list of all link-state PDUs in the IS-IS database. CSNPs are sent periodically on all links, and the receiving systems use the information in the CSNP to update and synchronize their link-state PDU databases.
It's actually AD because the CSNP only summarises LSPs in an index format, and routers may request a copy of the LSP using a PSNP if they are missing it.
CSNPs contain a complete description of all LSPs in the IS-IS database. IS-IS sends CSNPs periodically on all links
In my opinion this is A nd C. CSNPs are flooded every 10 seconds on LAN segmnet. CSNP contains descriptions of LSP. If neighbor router notices that something is missing, it is requesting via PSNP missing prefixes.
A & D************
A and C