OSPF DD Packet Content and Synchronization Mechanics
Short answer
A DD packets do not contain all LSA information but only LSA headers, and they are not used for periodic LSDB synchronization.
Question
Key Takeaways
The main trap is confusing DD packets with LSU packets; DD packets only summarize links via headers, while LSUs carry the full LSA details.
This question tests OSPF packet functions, specifically identifying that DD packets carry only LSA headers, not full LSA data, making statement A false.
Common mistake: Many candidates might think A is true because they associate 'synchronization' with DD packets. However, DD packets only initiate the process by exchanging headers; the actual data transfer happens later via LSU packets, and synchronization is not periodic.
Expert Analysis
The question asks to identify the false statement regarding OSPF packet types and behaviors. The core concept tested here is the distinction between the contents of Database Description (DD) packets versus Link State Update (LSU) packets.
Analysis of Option A: This statement claims that DD packets contain all LSA information and are used to periodically synchronize LSDB information. This is false. In OSPF, DD packets only carry LSA headers (summary information) to negotiate which full LSAs need to be exchanged. They do not contain the full LSA data. Furthermore, OSPF neighbors do not periodically synchronize their entire LSDB; they only exchange updates when changes occur or during initial adjacency formation using DD, LSU, and LSR packets. Full synchronization is achieved via DD followed by LSU packets containing the actual LSA bodies.
Analysis of Option D: This statement says DD packets carry LSA header information to describe link state summary information. This is true and directly contradicts the false claim in Option A. DD packets are indeed used for database description using headers only.
Analysis of Options B and C:
- Option B is true: Hello packets are used for neighbor discovery, maintenance, and DR/BDR election on broadcast/NBMA networks.
- Option C is true: For two routers to become neighbors, their Hello intervals (and Dead intervals, Router ID, Area ID, Authentication, etc.) must match. If the intervals differ, the adjacency will not form.
Therefore, Option A is the false statement because it misrepresents both the content of DD packets (claiming full LSA info instead of headers) and the synchronization mechanism (implying periodic full sync rather than change-based or initial-only sync).
Comments support this view, noting that DD packets only contain LSA headers.
Exam Strategy
When answering OSPF packet questions, strictly differentiate between the four packet types: Hello (neighbor/DR), DD (header summary), LSR (request specific LSAs), and LSU (full LSA data). Always check if a statement attributes 'full data' to a DD packet or 'periodic sync' to any single packet type, as these are common distractors.
Frequently Asked Questions
Do OSPF neighbors periodically synchronize their LSDB?
What exactly does an OSPF DD packet contain?
Community Votes
100% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 1 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 1
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Stevemy 👍 1 Answered Ales DD ne contienne que les entête des LSA
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