bin/.local/bin/cidr #!/bin/bash # CIDR - the CIDR block calc & cheatsheet # CC0 xero | https://x-e.ro | https://github.com/xero usage() { EXITCODE=0 if [ -n "" ] && [ "" -eq "" ] 2>/dev/null; then EXITCODE= fi me="$(basename "$(test -L "{{&blob}}" && readlink "{{&blob}}" || echo "{{&blob}}")")" echo "usage: ${me} [-c|-i IP CIDR|-n IP]" echo " [--chart] display the CIDR chart" echo " [--in IP CIDR] checks if an ip in a given CIDR" echo " [--netmask IP] returns the netmask of a given CIDR" exit "$EXITCODE" } # check if required commands/bins exist function isinstalled() { builtin type -P "" &> /dev/null || { echo >&2 "'' dependancy required"; exit 1 } } # print the CIDR cheatsheet chart() { cat << X0 Netmask Netmask (binary) CIDR Notes _____________________________________________________________________________ 255.255.255.255 11111111.11111111.11111111.11111111 /32 Host (single addr) 255.255.255.254 11111111.11111111.11111111.11111110 /31 Unuseable 255.255.255.252 11111111.11111111.11111111.11111100 /30 2 useable 255.255.255.248 11111111.11111111.11111111.11111000 /29 6 useable 255.255.255.240 11111111.11111111.11111111.11110000 /28 14 useable 255.255.255.224 11111111.11111111.11111111.11100000 /27 30 useable 255.255.255.192 11111111.11111111.11111111.11000000 /26 62 useable 255.255.255.128 11111111.11111111.11111111.10000000 /25 126 useable 255.255.255.0 11111111.11111111.11111111.00000000 /24 "Class C" 254 useable 255.255.254.0 11111111.11111111.11111110.00000000 /23 2x Class C's = 510 usable 255.255.252.0 11111111.11111111.11111100.00000000 /22 4x Class C's = 1022 usable 255.255.248.0 11111111.11111111.11111000.00000000 /21 8x Class C's = 2046 usable 255.255.240.0 11111111.11111111.11110000.00000000 /20 16x Class C's = 4094 usable 255.255.224.0 11111111.11111111.11100000.00000000 /19 32x Class C's = 8190 usable 255.255.192.0 11111111.11111111.11000000.00000000 /18 64x Class C's = 16382 usable 255.255.128.0 11111111.11111111.10000000.00000000 /17 128x Class C's = 32766 usable 255.255.0.0 11111111.11111111.00000000.00000000 /16 "Class B" 65534 usable 255.254.0.0 11111111.11111110.00000000.00000000 /15 2x Class B's = 131070 usable 255.252.0.0 11111111.11111100.00000000.00000000 /14 4x Class B's = 262142 usable 255.248.0.0 11111111.11111000.00000000.00000000 /13 8x Class B's = 524286 usable 255.240.0.0 11111111.11110000.00000000.00000000 /12 16x Class B's = 1048574 usable 255.224.0.0 11111111.11100000.00000000.00000000 /11 32x Class B's = 2097150 usable 255.192.0.0 11111111.11000000.00000000.00000000 /10 64x Class B's = 4194302 usable 255.128.0.0 11111111.10000000.00000000.00000000 /9 128x Class B's = 8388606 usable 255.0.0.0 11111111.00000000.00000000.00000000 /8 "Class A" 16777214 254.0.0.0 11111110.00000000.00000000.00000000 /7 252.0.0.0 11111100.00000000.00000000.00000000 /6 248.0.0.0 11111000.00000000.00000000.00000000 /5 240.0.0.0 11110000.00000000.00000000.00000000 /4 224.0.0.0 11100000.00000000.00000000.00000000 /3 192.0.0.0 11000000.00000000.00000000.00000000 /2 128.0.0.0 10000000.00000000.00000000.00000000 /1 0.0.0.0 00000000.00000000.00000000.00000000 /0 IP space Net Host Total Net Addr Addr Addr Number Class Range NetMask Bits Bits of hosts ---------------------------------------------------------- A 0-127 255.0.0.0 /8 24 16777216 (i.e. 114.0.0.0) B 128-191 255.255.0.0 /16 16 65536 (i.e. 150.0.0.0) C 192-254 255.255.255.0 /24 8 256 (i.e. 199.0.0.0) D 224-239 (multicast) E 240-255 (reserved) F 208-215 255.255.255.240 28 4 16 G 216/8 ARIN - North America G 217/8 RIPE NCC - Europe G 218-219/8 APNIC H 220-221 255.255.255.248 29 3 8 (reserved) K 222-223 255.255.255.254 31 1 2 (reserved) (ref: RFC1375 & http://www.iana.org/assignments/ipv4-address-space ) ( http://www.iana.org/numbers.htm ) ---------------------------------------------------------- X0 } # calcuate minimum netmask for a given ip netmask () { c=0 x=0$( printf '%o' ${1//./ } ) while [ "$x" -gt 0 ]; do let c+=$((x%2)) 'x>>=1' done echo /$c } # check if ip is inside a given cidr block inside() { [ -z "" ] && usage 1 [ -z "" ] && usage 1 IP= CIDR= isinstalled nmap if [ $(nmap -sL -n "$CIDR" | awk '/Nmap scan report/{print $NF}' | grep "$IP") ]; then echo "true" exit 0 else echo "false" exit 1 fi } # parse command arguments case "" in --chart|"chart"|-c) chart ;; --in|"in"|-i) inside "" "" ;; --netmask|"netmask"|-n) netmask "" ;; *) usage ;; esac # EOF
