IPv4 reference
IPv4 /25 prefix
IPv4 /25 prefix corresponds to /25, with 128 total addresses and 126 usable hosts.
Example network details for 0.0.0.0/25
- CIDR
- 0.0.0.0/25
- Prefix
- /25
- Network address
- 0.0.0.0
- Broadcast address
- 0.0.0.127
- First usable address
- 0.0.0.1
- Last usable address
- 0.0.0.126
- Subnet mask
- 255.255.255.128
- Wildcard mask
- 0.0.0.127
- Total addresses
- 128
- Usable hosts
- 126
Binary masks
Subnet: 11111111.11111111.11111111.10000000
Wildcard: 00000000.00000000.00000000.01111111
The first 25 bits identify the network. The remaining 7 bits identify addresses inside it.
First subdivision
Dividing this network into 4 equal blocks produces:
0.0.0.0/27— 30 usable hosts0.0.0.32/27— 30 usable hosts0.0.0.64/27— 30 usable hosts0.0.0.96/27— 30 usable hosts
Continue working with /25
What this result means
A /25 IPv4 network contains 128 consecutive addresses. The network and broadcast addresses are reserved in traditional LAN use, leaving 126 usable host addresses.
Use the wildcard mask in access lists and routing policy where a device expects inverse mask bits. Always verify vendor syntax before applying generated values to production equipment.