What a /22 subnet is: four /24s
A /22 holds 1,024 addresses, 1,022 usable, and contains exactly four /24 networks. It is the usual answer when a /24 is too small and a /20 is wasteful.
At a glance
- Subnet mask
- 255.255.252.0
- Wildcard mask
- 0.0.3.255
- Total addresses
- 1,024
- Usable hosts
- 1,022
- Contains
- 4 networks of /24
- Host bits
- 10 of 32
In detail
The mask is 255.255.252.0 and the third octet steps by 4. The broadcast address of a /22 is at the end of the fourth /24, which surprises people who expect it at the end of the first.
A good size for a subnet that has outgrown 254 hosts: a big office floor, a container host pool, a network of printers and sensors that multiplied.
Growing a /24 into a /22 requires the three /24s above it to be free and the block to start on a multiple of 4. Check that before promising the change, because renumbering is the alternative.
Examples
before: 10.2.4.0/24 10.2.4.0 to 10.2.4.255, 254 usable
after: 10.2.4.0/22 10.2.4.0 to 10.2.7.255, 1022 usable
absorbed: 10.2.5.0/24, 10.2.6.0/24, 10.2.7.0/24Things that catch people out
- 10.2.5.0/22 is not a network address. Only third octets divisible by 4 are.
- Widening the mask on the router without widening it on every host leaves the hosts thinking anything outside their old /24 needs the gateway, which usually still works and hides the misconfiguration until something breaks.
Try it: IP Subnet Calculator
Enter any IPv4 address with a prefix or a dotted mask and get the network address, broadcast address, wildcard mask, usable host range, address class, and the hex and binary forms.
IP Subnet Calculator
LOCAL · Browser-OnlyCalculate IP subnet details, network ranges, and CIDR notation
192.168.1.0192.168.1.255255.255.255.00.0.0.255192.168.1.0/24192.168.1.1 - 192.168.1.254192.168.1.1192.168.1.254256254C0xC0A8016411000000.10101000.00000001.01100100Split into two /25 subnets
Dividing 192.168.1.0/24 one prefix deeper.
Common Subnet Masks
Related IPv4 subnets
All ipv4 subnets →What a /24 subnet is: the classic LAN subnet
A /24 uses the mask 255.255.255.0 and gives 254 usable addresses. What it is for and where it goes wrong.
What a /23 subnet is: two /24s
A /23 uses the mask 255.255.254.0 and gives 510 usable addresses. What it is for and where it goes wrong.
What a /20 subnet is: sixteen /24s
A /20 uses the mask 255.255.240.0 and gives 4,094 usable addresses. What it is for and where it goes wrong.
What a /25 subnet is: half a /24
A /25 uses the mask 255.255.255.128 and gives 126 usable addresses. What it is for and where it goes wrong.
What a /26 subnet is: a quarter of a /24
A /26 uses the mask 255.255.255.192 and gives 62 usable addresses. What it is for and where it goes wrong.
What a /27 subnet is: an eighth of a /24
A /27 uses the mask 255.255.255.224 and gives 30 usable addresses. What it is for and where it goes wrong.
Tools for this
- IP Subnet Calculator Free online IP subnet calculator - calculate IP subnet details, CIDR notation, and network address ranges
- IP Address Lookup Free online IP address lookup - find your public IP address and basic network information
- Number Base Converter Free online number base converter - convert numbers between decimal, binary, octal, and hexadecimal