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This is a really nice post, thanks to all that contributed in this post.
I am doing an script that checks IPTABLES to see if there are IPs that could be joined in one CIDR notation up to the /24 no more than that and wish there could be something that could do this, but in the mean time this code will help me a lot.
Distribution: Red Hat Enterprise Linux, Mac OS X, Ubuntu, Fedora, FreeBSD
Posts: 89
Rep:
CIDR in base 10
For a class project I made a CIDR netmask calculator using base 10 math. I release this code into the public domain.
Code:
#!/bin/bash
# CIDR Netmask Calculator
y=$[2**(32-$1)] # y = 2^(32-x), x = CIDR class
printf "$1\t" # x
printf "$y\t" # y
if ! [ "$[$y/256**0]" -gt "256" ]; then # y
echo 255.255.255.$[256-($y/256**0)] # 256-(y)
exit
fi
if ! [ "$[$y/256**1]" -gt "256" ]; then # y/256
echo 255.255.$[256-($y/256**1)].0 # 256-(y/256)
exit
fi
if ! [ "$[$y/256**2]" -gt "256" ]; then # y/256/256
echo 255.$[256-($y/256**2)].0.0 # 256-(y/256/256)
exit
fi
if ! [ "$[$y/256**3]" -gt "256" ]; then # y/256/256/256
echo $[256-($y/256**3)].0.0.0 # 256-(y/256/256/256)
exit
fi
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