I want to make an IP scan using NMAP, but the operating time varies for some reason. The command can be executed in 2 seconds, and if I launch it again just after, it can take 30 seconds.

This is the command I use :

nmap -n -sn -T5 --max-rtt-timeout 1s

-n : no DNS resolution

-sn : disable port scan

-T5 fast mode

--max-rtt-timeout round trip timeout for the probes 1s

I don't know if my optimisation is good. How do I make it better ?

  • That would depend on what it is you are scanning Aug 28, 2015 at 6:41
  • 1
    run nmap -v or under strace to see if what nmap is wedging on is apparent?
    – user17308
    Aug 28, 2015 at 14:48


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