Distance-Vector vs. Link-State — Identify the True Statements Consider the following statements: Link-state sends its complete routing table out all active interfaces on periodic intervals. Distance-vector sends its complete routing table out all active interfaces on periodic intervals. Link-state sends updates containing the state of its own links to all routers in the internetwork. Distance-vector sends updates containing only the state of its own links to all routers in the internetwork. Which combination is correct?
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A1 only
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B3 only
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C2 and 3 only
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DNone of the above
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E1 and 4 only
Answer
Correct Answer: 2 and 3 only
Explanation
Introduction / Context:Routing protocols differ in how they disseminate information. Distance-vector protocols share entire tables periodically, while link-state protocols advertise link-state information (LSAs) and build a full topology locally. Distinguishing these behaviors is vital for predicting convergence and bandwidth use.
Given Data / Assumptions:
- Distance-vector examples: RIP, IGRP.
- Link-state examples: OSPF, IS-IS.
- Periodic vs. event-driven updates must be understood correctly.
Concept / Approach:Statement 2 is true: distance-vector protocols periodically send their routing tables (in RIP, every 30 seconds). Statement 3 is true: link-state protocols flood link-state advertisements about their own links; routers then compute shortest paths using algorithms like Dijkstra. Statement 1 is false because link-state does not send full routing tables periodically; instead, LSAs are sent on changes and at refresh intervals, not wholesale tables. Statement 4 is false for distance-vector because DV does not send only link states; it sends distance vectors (routes and metrics), not raw link-state data to all routers.
Step-by-Step Solution:Classify each statement as DV or LS.Mark 2 (DV periodic full table) as true.Mark 3 (LSA flooding of link states) as true.Mark 1 and 4 as false based on protocol mechanics.Select “2 and 3 only.”
Verification / Alternative check:Protocol RFCs and textbooks confirm DV periodic timers and LS flooding mechanisms with separate SPF computations.
Why Other Options Are Wrong:
- 1 only: Misstates link-state behavior.
- 3 only: Ignores the truth of 2.
- None: Incorrect because 2 and 3 are true.
- 1 and 4: Both are false.
Common Pitfalls:Assuming link-state sends “routing tables”; it sends LSAs, not computed final routes.
Final Answer:2 and 3 only