IP Subnet Calculator
IP Address:
. . .
Subnet mask/bits in mask:
Subnets to display:

IP address:
IP class: A
Subnet mask:
Subnet address:
Bits in mask: 24
Number of hosts: 254
Subnet addr First host Last host Subnet mask Broadcast

This subnet calculator can help you with the following tasks:

  • Identify subnet parameters for a given IP address and subnet mask (or CIDR prefix).
  • Display subnet parameters for a number of consecutive subnets of the specified length.
CIDR stands for Classless Inter-Domain Routing. CIDR refers to a method for allocating IP addresses and routing Internet Protocol packets.

Number of hosts on a /31 subnet:
Generally, within a subnet, two host addresses - all-zeros and one all-ones are reserved as network address and broadcast, respectively. The same approach applied to a /31 subnet with only two possible addresses in the host identifier would leave no usable addresses for host assignment. RFC3021: Using 31-Bit Prefixes on IPv4 Point-to-Point Links allows assignment of the all-zeros and one all-ones IP addresses to hosts on point-to-point links.