In a broadcast network, what mechanism does the IS-IS protocol use to ensure the reliability of neighbor relationship establishment?

Question

Options

• AStatus synchronization
• BThree-way handshake
• CChecksum
• DThree-way handshakes

• A
  13% (4)
• B
  10% (3)
• C
  3% (1)
• D
  73% (22)

Explanation

Option D is correct because IS-IS uses a three-way handshake process to reliably establish neighbor adjacencies on broadcast networks. Each router sends Hello PDUs that include a list of neighbors it has already heard from; a full adjacency is only formed when both routers confirm they can hear each other, completing the three-stage exchange and ensuring bidirectional reachability before the relationship is considered up.

Option A (Status synchronization) describes the process of synchronizing link-state databases between neighbors after adjacency is established, not the mechanism that establishes the adjacency itself. Option C (Checksum) is a data integrity tool embedded in IS-IS PDUs to detect corruption, but it plays no role in the neighbor establishment handshake logic. Option B (Three-way handshake, singular) is a near-identical distractor designed to test precision; in broadcast networks IS-IS performs three-way handshakes (plural) with multiple neighbors simultaneously, making D the more accurate and complete description of the mechanism.

Memory tip: Think of IS-IS neighbor establishment as "I hear you, you hear me, we agree" -- three steps, just like a handshake between two parties who must both confirm the greeting before proceeding.

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