GATE 2010 CS (CS1) – Question 65

Computer Networks · Routing: Distance Vector and Link State Routing · 2 marks · Multiple choice

The network uses distance-vector routing and is initialized with direct-link costs. Wait for convergence after each change. First identify the unused links in the original network shown. Change each of those links to cost 2 and reconverge. How many links are now unused?

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Correct answer: (B) 1

Explanation

The original unused links R1–R2 and R4–R6 now each cost two. R5–R6 still costs four, but the new alternative R5→R4→R6 costs 1+2=3, making it unused. Each other direct link remains a shortest route between its endpoints. Hence there is one unused link, B.

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