The GATE Grind

GATE 2024 CS (CS1) – Question 31

Computer Networks · IPv4: Addressing, CIDR, Fragmentation and NAT · 1 mark · Multiple select

Which of the following fields is/are modified in the IP header of a packet going out of a network address translation (NAT) device from an internal network to an external network?

  1. Source IP
  2. Destination IP
  3. Header Checksum
  4. Total Length

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Show answer and explanation

Correct answer: (A) Source IP; (C) Header Checksum

Explanation

NAT rewrites the source IP for outgoing packets, which forces recomputation of the IP header checksum. Destination IP and total length are unchanged.