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I am running a traceroute command to host [YYY.YYY.Y.Y], and at the output is as follows:

...
e1-25-20-cr-rt-bb2-area2.ns.uwaterloo.ca (ZZZ.ZZ.ZZ.ZZ)  4.164 ms  6.741 ms  6.444 ms
 8  wms.uwaterloo.ca (MMM.MM.MMM.MM)  3.034 ms  3.612 ms  3.334 ms
 9  wms.uwaterloo.ca (MMM.MM.MMM.MM)  3.802 ms !N  5.354 ms !N  5.588 ms !N

Several sources have told me that !N means that the destination host is unreachable. However, this seems to be the case when the output is as follows:

9 wms.uwaterloo.ca (129.97.208.23) !N !N !N

What does it mean when !N appears beside an elapsed time ?

I don't think I should be interpreting {elapsed_time} !N as destination unreachable since I was definitely able to reach my target destination through a web browser and through "ping".

Universal Thinker
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1 Answers1

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wms.uwaterloo.ca sends back an ICMP Destination network unreachable message. Some protocols and port used by your traceroute are filtered. If you can create a packet capture then you will see and understand what happens under the hood.

Gábor
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