/25 Subnet Mask (255.255.255.128)
| Prefix | /25 |
|---|---|
| Subnet mask | 255.255.255.128 |
| Wildcard mask | 0.0.0.127 |
| Binary mask | 11111111.11111111.11111111.10000000 |
| Total addresses | 128 |
| Usable hosts | 126 |
| Host bits | 7 |
| Subnets of /25 in a /24 | 2 |
| Block size | 128 addresses (subnets start every 128 in the last octet) |
e.g. 10.0.0.5/22 or 10.0.0.5 255.255.252.0
| Network address | 192.168.1.0 | |
|---|---|---|
| Broadcast address | 192.168.1.127 | |
| First usable host | 192.168.1.1 | |
| Last usable host | 192.168.1.126 | |
| Total addresses | 128 | |
| Usable hosts | 126 | |
| Subnet mask | 255.255.255.128 | |
| Wildcard mask | 0.0.0.127 | |
| CIDR notation | 192.168.1.0/25 | |
| IP class | Class C (legacy) | |
| Address type | Private (RFC 1918) | |
| IP address (binary) | 11000000.10101000.00000001.00000000 | |
| Subnet mask (binary) | 11111111.11111111.11111111.10000000 |
■ network bits ■ host bits
| Requested hosts | CIDR | First host | Last host | Broadcast | Usable hosts |
|---|
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What is a /25 subnet?
A /25 subnet uses the first 25 bits of an IPv4 address for the network and leaves 7 bits for hosts. Its subnet mask is 255.255.255.128, and it contains 2⁷ = 128 addresses, of which 126 can be assigned to devices. Typical use: Splitting a /24 into halves or quarters for separate VLANs. Use the subnet calculator above to check any /25 network.
/25 subnet example
For 192.168.1.0/25: network address 192.168.1.0, usable hosts 192.168.1.1 – 192.168.1.126, broadcast address 192.168.1.127, wildcard mask 0.0.0.127.
/25 networks in 192.168.1.0/24
A /24 holds 2 /25 networks:
- 192.168.1.0/25
- 192.168.1.128/25
Frequently asked questions
How many usable IPs are in a /25?
126. The block has 128 addresses; the first is the network address and the last is the broadcast address.
What is the subnet mask for /25?
255.255.255.128, or 11111111.11111111.11111111.10000000 in binary.
How many /25 subnets are in a /24?
2 (2¹), because a /25 uses 1 more network bits than a /24.
What is the difference between /25 and /24?
A /24 (255.255.255.0) is twice as large: 256 addresses and 254 usable hosts, spanning two consecutive /25 blocks such as 192.168.1.0–192.168.1.255.