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/25 Subnet Mask: 255.255.255.128

A /25 prefix fixes the first 25 bits of the address as the network, leaving 7 bits for hosts. That gives 128 addresses, of which 126 can be assigned to hosts.

CIDR notation/25
Subnet mask255.255.255.128
Wildcard mask0.0.0.127
Binary mask11111111.11111111.11111111.10000000
Hex mask0xFFFFFF80
Total addresses128
Usable hosts126

Example: 192.168.1.0/25

  • Network address: 192.168.1.0
  • First usable host: 192.168.1.1
  • Last usable host: 192.168.1.126
  • Broadcast address: 192.168.1.127

When to use a /25 subnet

Small office networks or VLANs for a single team or device class, often created by splitting a /24 into equal parts.

  • 131,072 /25 subnets fit in a /8.
  • 512 /25 subnets fit in a /16.
  • 2 /25 subnets fit in a /24.

Frequently Asked Questions

What is the subnet mask for /25?

The subnet mask for /25 is 255.255.255.128, and its wildcard (inverse) mask is 0.0.0.127.

How many hosts are in a /25?

A /25 contains 128 addresses. Subtracting the network and broadcast addresses leaves 126 usable hosts.