Option A (Correct):
Complete Sequence Number PDUs (CSNPs) are periodically flooded by the Designated Intermediate System (DIS) on multi-access networks (e.g., Ethernet).
[Reference: Juniper IS-IS CSNP Overview., Option C (Correct):, Partial Sequence Number PDUs (PSNPs) contain only the headers (descriptions) of LSPs (e.g., LSP ID, sequence number, checksum)., PSNPs are used to:, Request missing LSPs (when a router detects discrepancies via CSNPs)., Acknowledge LSP receipt (in point-to-point networks)., They do not include the full LSP data., Reference: Juniper IS-IS PSNP Overview., , Why Other Options Are Incorrect:, Option B: Incorrect. PSNPs are not flooded periodically—they are sent on-demand for specific LSP synchronization., Option D: Incorrect. While CSNPs do contain LSP descriptions (headers), the term "only" is misleading. CSNPs summarize all LSPs in the LSDB, but they are not limited to "only" descriptions—they serve as a complete database overview., , Key Takeaways:, CSNPs are periodic, broadcast by the DIS, and ensure LSDB consistency., PSNPs are triggered, contain specific LSP headers, and handle requests/acknowledgments., IS-IS uses CSNPs and PSNPs to maintain efficient LSDB synchronization without flooding full LSPs unnecessarily., For further details, refer to Juniper’s official IS-IS documentation:Juniper IS-IS Configuration Guide., , ]
