nmap: easily Ping-Scan all addresses in my subnet

Question

Is there an nmap line that will auto-detect my current IP address and subnet mask, and run a ping-scan on all? For example:

#> nmap -sP 0.0.0.0

Instead of manually:

#> nmap -sP 192.168.100.0/24

Answer 1

I don't think that there is a way with doing that with nmap alone, but you could script it: Here is a quick and dirty solution:

#!/bin/bash

IP_AND_MASK=`ifconfig | grep "inet addr" | head -n1 | sed 's|.*addr:\([0-9\.]*\).*Mask:\([0-9\.]*\)|\1/\2|g'`
NETWORK=`ipcalc "$IP_AND_MASK" | grep "Network:" | sed 's|^Network:\s*\([0-9/\.]*\).*|\1|g'`
nmap -sP "$NETWORK"

You have to install ipcalc to make that solution work.

hth

Answer 2

Mileage may vary, but this should work well in most circumstances...

nmap -sP `hostname -I | sed 's/[0-9]\+\s/0\/24 /g'`

Answer 3

This works, but then you still need to know your own subnet... saves copy-pasting the IP address though.

nmap -sP /24