IPv4 reference
IPv4 /31 prefix
IPv4 /31 prefix corresponds to /31, with 2 total addresses and 2 usable hosts.
Example network details for 0.0.0.0/31
- CIDR
- 0.0.0.0/31
- Prefix
- /31
- Network address
- 0.0.0.0
- Broadcast address
- 0.0.0.1
- First usable address
- 0.0.0.0
- Last usable address
- 0.0.0.1
- Subnet mask
- 255.255.255.254
- Wildcard mask
- 0.0.0.1
- Total addresses
- 2
- Usable hosts
- 2
Binary masks
Subnet: 11111111.11111111.11111111.11111110
Wildcard: 00000000.00000000.00000000.00000001
The first 31 bits identify the network. The remaining 1 bits identify addresses inside it.
First subdivision
Dividing this network into 2 equal blocks produces:
0.0.0.0/32— 1 usable hosts0.0.0.1/32— 1 usable hosts
Continue working with /31
What this result means
A /31 IPv4 network contains 2 consecutive addresses. For /31, point-to-point and host-route rules differ from traditional subnet reservations.
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.