/31 Subnet

A /31 has 2 addresses. Its netmask is 255.255.255.254. Enter any address below to see its /31 network.

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IP Address / Prefix

Examples:

IPv4 network

2 usable hosts · 192.168.1.0 to 192.168.1.1

Private (RFC 1918)

Details

Netmask

Wildcard Mask

First Usable

Last Usable

Usable HostsPoint-to-point link (RFC 3021)

Total Addresses

Netmask in Binary

Split Into Subnets

192.168.1.0/32192.168.1.0 – 192.168.1.0

192.168.1.1/32192.168.1.1 – 192.168.1.1

Subnet Calculator

/31 at a glance

CIDR Prefix/31

Netmask255.255.255.254

Wildcard Mask0.0.0.1

Netmask (Hex)0xFFFFFFFE

Total Addresses2

Usable Hosts2

Host Bits1

Fit in a /24128

Binary Mask11111111.11111111.11111111.11111110

A /31 fixes the first 31 bits of the address as the network and leaves 1 bits for hosts, so it holds 2^1 = 2 addresses. On point-to-point links both are usable, as there is no network or broadcast address (RFC 3021).

Two addresses, both usable on point-to-point links (RFC 3021). Saves half the addresses compared with a /30 on router links.

Most networks filter BGP announcements longer than /24, so a block this size cannot be routed on the internet on its own; it is carved out of a larger block by your provider.

Other IPv4 Prefixes