Traceroute and meaning of outputs

Van Jacobson is a prominent person in networking, especially for TCP/IP. What I didn’t know was (according to wikipedia) original traceroute was also written by him. As this tool is the swiss knife of a Tech Support Engineer, I would like to share the meaning of some of the outputs. If you have any other error, please do share here to improve the list.


This sample output indicates that network that IP belongs doesn’t exist on the host if you take a packet capture when you see this error, you will see that you receive, ICMP destination unreachable “Network Unreachable” message from this host.


This error however indicates that IP network is available but the individual host can’t be reached. It isn’t available. The last host ( which is supposed to provide connectivity to the destination device returns ICMP destination unreachable “Host unreachable” to the source host.


This error is received if you are trying some PMTU discovery. Intermediate host which can’t deliver this oversized packet returns ICMP Destination unreachable “Fragmentation needed and DF bit set”

Any other error letter you have seen? Drop your comment here!

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