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GATE 2021 CS (CS2) – Question 55

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

Distance-vector router R has neighbours X,Y,Z with link costs 3,2,5. Their advertised distances to P are 7,6,5 and to Q are 4,6,8. R initially does not know routes to P,Q. Which entries result after this iteration?

Diagram for GATE 2021 CS (CS2) question 55
  1. Distance R→P is 10
  2. Distance R→Q is 7
  3. Next hop to P is Y
  4. Next hop to Q is Z

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Show answer and explanation

Correct answer: (B) Distance R→Q is 7; (C) Next hop to P is Y

Explanation

For P, the candidate costs via X,Y,Z are 3+7=10, 2+6=8, 5+5=10; choose eight via Y. For Q they are 3+4=7, 2+6=8, 5+8=13; choose seven via X. Thus B and C hold.

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