When analyzing traceroute output, what does a consistent timeout (" *") at a specific hop indicate?

The correct answer is B. ICMP rate limiting or firewall block. Traceroute works by sending packets with incrementing TTL values and listening for ICMP 'Time Exceeded' responses from each hop. When a specific hop consistently returns ' *', it means that device is either rate-limiting or blocking ICMP responses - a common firewall or ACL polic

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Question

When analyzing traceroute output, what does a consistent timeout ("* * *") at a specific hop indicate?

Options

ADNS misconfiguration
BICMP rate limiting or firewall block
CPacket fragmentation
DMTU discovery failure

How the community answered

(34 responses)

A
6% (2)
B
88% (30)
C
3% (1)
D
3% (1)

Explanation

Traceroute works by sending packets with incrementing TTL values and listening for ICMP 'Time Exceeded' responses from each hop. When a specific hop consistently returns '* * *', it means that device is either rate-limiting or blocking ICMP responses - a common firewall or ACL policy to prevent network topology reconnaissance. The key word is 'consistent' at one specific hop: traffic continues beyond that hop (subsequent hops may respond), confirming it is a policy decision at that device, not a routing failure. DNS misconfiguration (A), packet fragmentation (C), and MTU discovery failure (D) do not produce this specific traceroute pattern.

Topics

#Traceroute analysis#ICMP#Network troubleshooting#Firewall rules

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