Subnetting and CIDR

An IPv4 address is 32 bits and a prefix length draws one line through them. Everything else — network, broadcast, host range, "is it local?" — is an AND or an OR.

Network = IP AND mask

Broadcast = network OR NOT mask

Hosts = 2^h − 2

Host APrefix /26Host B

Presets

Animation Speed: 1400ms

Step 1 of 8192.168.10.77/26

host A192.168.10.77

192.168.10.77 is how people write it, but a router sees 32 bits: four 8-bit octets, each written as a number from 0 to 255. Every subnet calculation is a bit operation on these 32 bits.

Prefix Cheat Sheet

/8255.0.0.016,777,214 hosts

/16255.255.0.065,534 hosts

/20255.255.240.04,094 hosts

/24255.255.255.0254 hosts

/26255.255.255.19262 hosts

/27255.255.255.22430 hosts

/28255.255.255.24014 hosts

/29255.255.255.2486 hosts

/30255.255.255.2522 hosts

/31255.255.255.2542 hosts

/32255.255.255.2551 hosts

Knowledge Check

Question 1 of 3

How many usable host addresses does a /26 subnet have?

DSAverse

Subnetting and CIDR

Prefix Cheat Sheet

Knowledge Check

See also

Subnetting and CIDR

Prefix Cheat Sheet

Knowledge Check

See also