Subnet Cheat Sheet

Subnet Cheat Sheet

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IPv4 Subnet Cheat Sheet

CIDR

Subnet Mask

Total IPs

Usable IPs

/32 255.255.255.255 1 1
/31 255.255.255.254 2 2*
/30 255.255.255.252 4 2
/29 255.255.255.248 8 6
/28 255.255.255.240 16 14
/27 255.255.255.224 32 30
/26 255.255.255.192 64 62
/25 255.255.255.128 128 126
/24 255.255.255.0 256 254
/23 255.255.254.0 512 510
/22 255.255.252.0 1024 1022
/21 255.255.248.0 2048 2046
/20 255.255.240.0 4096 4094
/19 255.255.224.0 8192 8190
/18 255.255.192.0 16,384 16,382
/17 255.255.128.0 32,768 32,766
/16 255.255.0.0 65,536 65,534
/15 255.254.0.0 131,072 131,070
/14 255.252.0.0 262,144 262,142
/13 255.248.0.0 524,288 524,286
/12 255.240.0.0 1,048,576 1,048,574
/11 255.224.0.0 2,097,152 2,097,150
/10 255.192.0.0 4,194,304 4,194,302
/9 255.128.0.0 8,388,608 8,388,606
/8 255.0.0.0 16,777,216 16,777,214
/7 254.0.0.0 33,554,432 33,554,430
/6 252.0.0.0 67,108,864 67,108,862
/5 248.0.0.0 134,217,728 134,217,726
/4 240.0.0.0 268,435,456 268,435,454
/3 224.0.0.0 536,870,912 536,870,910
/2 192.0.0.0 1,073,741,824 1,073,741,822
/1 128.0.0.0 2,147,483,648 2,147,483,646
*See rfc 3021

Private IP ranges

Class Size Subnet Mask Range of IPs
Class A 10.0.0.0/8 255.0.0.0 10.0.0.0 – 10.255.255.255
Class B 172.16.0.0/12 255.240.0.0 172.16.0.0 – 172.31.255.255
Class C 192.168.0.0/16 255.255.0.0 192.168.0.0 – 192.168.255.255

IPv6

Prefix

/48s

/56s

/64s

/24 16M 4G 1T
/25 8M 2G 512G
/26 4M 1G 256G
/27 2M 512M 128G
/28 1M 256M 64G
/29 512K 128M 32G
/30 256K 64M 16G
/31 128K 32M 8G
/32 64K 16M 4G
/33 32K 8M 2G
/34 16K 4M 1G
/35 8K 2M 512M
/36 4K 1M 256M
/37 2K 512K 128M
/38 1K 256K 64M
/39 512 128K 32M
/40 256 64K 16M
/41 128 32K 8M
/42 64 16K 4M
/43 32 8K 2M
/44 16 4K 1M
/45 8 2K 512K
/46 4 1K 256K
/47 2 512 128K
/48 1 256 64K
/49 128 32K
/50 64 16K
/51 32 8K
/52 16 4K
/53 8 2K
/54 4 1K
/55 2 512
/56 1 256
/57 128
/58 64
/59 32
/60 16
/61 8
/62 4
/63 2
/64 1

IPv6 bit mapping

IPv6 Bit Mapping

Binary

Bit 1 1 1 1 1 1 1 1
Bit Value 128 64 32 16 8 4 2 1
IPv4 Subnetting Cheat Sheet IPv6 Subnetting Cheat Sheet OSI, TCP/IP layer Cheat Sheet

Learning how to subnet is key to passing the CCNA, understanding how the internet works and the basis for any networking career.

You can practice with our IPv4 subnetting practice and IPv6 subnetting practice questions

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