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/12 Subnet Mask: 255.240.0.0

A /12 prefix fixes the first 12 bits of the address as the network, leaving 20 bits for hosts. That gives 1,048,576 addresses, of which 1,048,574 can be assigned to hosts.

CIDR notation/12
Subnet mask255.240.0.0
Wildcard mask0.15.255.255
Binary mask11111111.11110000.00000000.00000000
Hex mask0xFFF00000
Total addresses1,048,576
Usable hosts1,048,574

Example: 10.0.0.0/12

  • Network address: 10.0.0.0
  • First usable host: 10.0.0.1
  • Last usable host: 10.15.255.254
  • Broadcast address: 10.15.255.255

When to use a /12 subnet

Very large private networks. 10.0.0.0/8 is the largest private IPv4 range defined by RFC 1918.

  • 16 /12 subnets fit in a /8.

Frequently Asked Questions

What is the subnet mask for /12?

The subnet mask for /12 is 255.240.0.0, and its wildcard (inverse) mask is 0.15.255.255.

How many hosts are in a /12?

A /12 contains 1,048,576 addresses. Subtracting the network and broadcast addresses leaves 1,048,574 usable hosts.