I have multiple machines on my home network with a range of private IPs from to When I scan the network, I use:

nmap -v

But the console shows this:

Starting Nmap 7.01 at .... 
Initiating Ping Scan at ...
Scanning 512 hosts (4 ports/host)

I don't understand, it should scan 255^3 hosts, no?

  • @aurelien75000 if your machine is only attached to 2 class C networks, then nmap might only see the 2 networks and limit the scan to those
    – schroeder
    Mar 27, 2016 at 22:44
  • @schroeder ok, so how can i see if my machine is attached to 2 class C network ? ('i don't know what it means actually) Mar 27, 2016 at 22:46

1 Answer 1


When scanning a large range of IP addresses, NMAP will divide it into groups and scan each group and provide feedback after each one. This way the user can monitor it as it progresses:

Reference: NMAP https://nmap.org/book/man-performance.html

  • Thanks, indeed after the 1st 512 hosts it says it's going to scan 64 hosts (but 1000 ports scanning this time), i don"t understand actually Mar 27, 2016 at 22:57
  • 1
    @aurelien75000 4 ports/host is 4 host detection probes (a.k.a. "ping scan"). Host discovery uses larger hostgroups. When that finishes, it scans for open ports (1000 ports/host) using smaller groups of targets. Mar 28, 2016 at 18:33

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