Subnet mask cheat sheet

Posted: September 7, 2012 in Networking

As I’m not always dealing with networks and subnet masks, whenever I do end up needing to, I can never easily remember the conversions from subnet mask (dotted decimal) to the /?? format (CIDR). Found this table that is a great cheat sheet.
Netmasks
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 Unusable
255.255.255.252 11111111.11111111.11111111.11111100 /30 2 usable
255.255.255.248 11111111.11111111.11111111.11111000 /29 6 usable
255.255.255.240 11111111.11111111.11111111.11110000 /28 14 usable
255.255.255.224 11111111.11111111.11111111.11100000 /27 30 usable
255.255.255.192 11111111.11111111.11111111.11000000 /26 62 usable
255.255.255.128 11111111.11111111.11111111.10000000 /25 126 usable
255.255.255.0 11111111.11111111.11111111.00000000 /24 “Class C” 254 usable
255.255.254.0 11111111.11111111.11111110.00000000 /23 2 Class C’s
255.255.252.0 11111111.11111111.11111100.00000000 /22 4 Class C’s
255.255.248.0 11111111.11111111.11111000.00000000 /21 8 Class C’s
255.255.240.0 11111111.11111111.11110000.00000000 /20 16 Class C’s
255.255.224.0 11111111.11111111.11100000.00000000 /19 32 Class C’s
255.255.192.0 11111111.11111111.11000000.00000000 /18 64 Class C’s
255.255.128.0 11111111.11111111.10000000.00000000 /17 128 Class C’s
255.255.0.0 11111111.11111111.00000000.00000000 /16 “Class B”
255.254.0.0 11111111.11111110.00000000.00000000 /15 2 Class B’s
255.252.0.0 11111111.11111100.00000000.00000000 /14 4 Class B’s
255.248.0.0 11111111.11111000.00000000.00000000 /13 8 Class B’s
255.240.0.0 11111111.11110000.00000000.00000000 /12 16 Class B’s
255.224.0.0 11111111.11100000.00000000.00000000 /11 32 Class B’s
255.192.0.0 11111111.11000000.00000000.00000000 /10 64 Class B’s
255.128.0.0 11111111.10000000.00000000.00000000 /9 128 Class B’s
255.0.0.0 11111111.00000000.00000000.00000000 /8 “Class A”
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 “Class E” (Multicast and reserved)
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

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Comments
  1. I love what you guys are usually up too. Such clever
    work and reporting! Keep up the good works guys I’ve included you guys to my own blogroll.

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