Which statement is true about IS-IS PDUs?

The statement that separate CSNP and PSNP types exist for Level 1 and Level 2 systems is accurate. In the Intermediate System to Intermediate System (IS-IS) protocol, there are two levels of routing: Level 1, which is used for intra-area routing, and Level 2, which is used for inter-area routing.

Each of these levels has its own specific set of Protocol Data Units (PDUs) for communicating link-state information. The Complete Sequence Number PDU (CSNP) and the Partial Sequence Number PDU (PSNP) are utilized to manage the link-state database (LSDB) exchanges and ensure that routers within a given level maintain synchronized databases.

When Level 1 or Level 2 routers exchange link-state information, they utilize the respective CSNPs and PSNPs tailored for their operational context, thus ensuring efficient and accurate routing within their domains. Understanding this distinction is crucial for configuring IS-IS in a way that is optimized for both intra-area and inter-area communications.