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GSEC · Question #382

When trace route fails to get a timely response for a packet after three tries, which action will it take?

The correct answer is D. It will print '* * *' for the attempts, increment the TTL and try again until the maximum hop count. When traceroute receives no response for all three probes at a hop, it prints ' *' and increments the TTL to continue probing the next hop until the maximum hop count is reached.

Networking and Core Concepts

Question

When trace route fails to get a timely response for a packet after three tries, which action will it take?

Options

  • AIt will print '* * *' for the attempts and increase the maximum hop count by one.
  • BIt will exit gracefully, and indicate to the user that the destination is unreachable.
  • CIt will increase the timeout for the hop and resend the packets.
  • DIt will print '* * *' for the attempts, increment the TTL and try again until the maximum hop count.

How the community answered

(46 responses)
  • A
    7% (3)
  • B
    2% (1)
  • C
    11% (5)
  • D
    80% (37)

Why each option

When traceroute receives no response for all three probes at a hop, it prints '* * *' and increments the TTL to continue probing the next hop until the maximum hop count is reached.

AIt will print '* * *' for the attempts and increase the maximum hop count by one.

Traceroute increments the TTL to probe the next hop - it does not increase the maximum hop count, which is a fixed ceiling, not a dynamic value.

BIt will exit gracefully, and indicate to the user that the destination is unreachable.

Traceroute does not exit when a single hop is unresponsive; it continues sending probes with higher TTL values to find subsequent hops.

CIt will increase the timeout for the hop and resend the packets.

Traceroute does not retry the same hop with a longer timeout after three failed probes; it moves on to the next hop by incrementing the TTL.

DIt will print '* * *' for the attempts, increment the TTL and try again until the maximum hop count.Correct

Traceroute sends three UDP or ICMP probes per TTL value. If no ICMP Time Exceeded reply is received within the timeout period for all three probes, it prints '* * *' to represent the unresponsive hop. It then increments the TTL by one and probes the next hop, continuing this behavior until the destination responds or the maximum hop count (default 30) is exhausted.

Concept tested: Traceroute behavior on unresponsive hops

Source: https://linux.die.net/man/8/traceroute

Topics

#traceroute#TTL#network diagnostics#ICMP

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