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GATE CSE 2020 Q25: True statements about an IP router's forwarding behaviour

Question

Consider the following statements about the functionality of an IP based router.

I. A router does not modify the IP packets during forwarding.

II. It is not necessary for a router to implement any routing protocol.

III. A router should reassemble IP fragments if the MTU of the outgoing link is larger than the size of the incoming IP packet.

Which of the above statements is/are TRUE?

Try it: multiple choice: exactly one correct option

Select one option
Wrong answer costs 1/3 mark in GATE.
Show answer and explanation

Answer: D (official GATE 2020 final answer key)

Concept used: Routers decrement TTL and recompute the checksum; reassembly happens only at the destination; static routes need no routing protocol.

First step: Ask what a router changes in every forwarded IP header (TTL, checksum) and who reassembles fragments.

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Source: official GATE 2020 CS question paper and final answer key, organised by IIT Delhi. Question paper · Answer key

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