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/0 Subnet Mask: 0.0.0.0

A /0 prefix fixes the first 0 bits of the address as the network, leaving 32 bits for hosts. That gives 4,294,967,296 addresses, of which 4,294,967,294 can be assigned to hosts.

CIDR notation/0
Subnet mask0.0.0.0
Wildcard mask255.255.255.255
Binary mask00000000.00000000.00000000.00000000
Hex mask0x00000000
Total addresses4,294,967,296
Usable hosts4,294,967,294

Example: 0.0.0.0/0

  • Network address: 0.0.0.0
  • First usable host: 0.0.0.1
  • Last usable host: 255.255.255.254
  • Broadcast address: 255.255.255.255

When to use a /0 subnet

The entire IPv4 address space. 0.0.0.0/0 means "any address" and is used for default routes and allow-all firewall rules.

Frequently Asked Questions

What is the subnet mask for /0?

The subnet mask for /0 is 0.0.0.0, and its wildcard (inverse) mask is 255.255.255.255.

How many hosts are in a /0?

A /0 contains 4,294,967,296 addresses. Subtracting the network and broadcast addresses leaves 4,294,967,294 usable hosts.