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/32 subnet mask (255.255.255.255)

A /32 network has 0 host bits, 1 address and 1 usable host. It is 1/256 of a /24.

/32 at a glance

Netmask
255.255.255.255
Wildcard mask
0.0.0.0
Hex mask
0xFFFFFFFF
Binary mask
11111111.11111111.11111111.11111111
Host bits
0
Total addresses
1
Usable hosts
1
Compared with a /24
1/256 of a /24
Calculate a /32 in the subnet calculator

Typical uses of a /32

A /32 is a single address. You use it for host routes, router loopback addresses, firewall or security-group rules that allow exactly one IP, BGP blackhole (RTBH) announcements, and the instance metadata address 169.254.169.254.

Well-known /32 blocks

  • 255.255.255.255/32: Limited broadcast (RFC 919)
  • 169.254.169.254/32: Instance metadata service on AWS, Azure, GCP and others

Example /32 ranges

NetworkNetwork addressFirst usableLast usableBroadcastNext /32
10.0.0.0/32 10.0.0.0 10.0.0.0 10.0.0.0 none 10.0.0.1/32 calculate
172.16.0.0/32 172.16.0.0 172.16.0.0 172.16.0.0 none 172.16.0.1/32 calculate
192.168.1.0/32 192.168.1.0 192.168.1.0 192.168.1.0 none 192.168.1.1/32 calculate
203.0.113.0/32 203.0.113.0 203.0.113.0 203.0.113.0 none 203.0.113.1/32 calculate

How many /32s fit

In aNumber of /32 subnets
/816,777,216
/1665,536
/204,096
/24256
/2816

/32 in AWS, Azure and Google Cloud

PlatformAllowed subnet sizes/32 allowed?Usable after reservation
AWS VPC/16 to /28 No -
Azure VNet/2 to /29 No -
Google Cloud VPC/4 to /29 No -

Cloud providers reserve addresses in every subnet (first four and the last address (network, VPC router, DNS, future use, broadcast) on AWS), so the usable count there differs from the classic 2^n - 2.