The /8 subnet
A /8 subnet uses the mask 255.0.0.0 and holds 16,777,216 addresses, 16,777,214 of them usable.
A /8 is a very large IPv4 block. Its mask is 255.0.0.0 and it holds 16,777,216 addresses, which puts it at the scale of a regional allocation or an entire private supernet rather than a single LAN.
Networks this size are almost always carved into smaller subnets before use. You will see a /8 as an aggregate route or a private-address supernet such as 10.0.0.0/8, not as a single broadcast domain.
Below you can see the exact network, broadcast, and host range for any /8 you enter, calculated instantly in your browser.
Calculate a /8 network
Accepts CIDR (192.0.2.0/24), IP + mask (192.0.2.0 255.255.255.0), or a bare IP (defaults to /24).
00001010.00000000.00000000.0000000011111111.00000000.00000000.00000000Example: 10.0.0.0/8
Taking 10.0.0.0/8 as a worked example, the block breaks down like this:
| Network address | 10.0.0.0 |
|---|---|
| Usable range | 10.0.0.1 - 10.255.255.254 |
| Broadcast address | 10.255.255.255 |
| Total addresses | 16,777,216 |
| Usable hosts | 16,777,214 |
| Size | 1 class A block (a /8) |
Frequently asked questions
What is the subnet mask for a /8?
A /8 uses the subnet mask 255.0.0.0. Its wildcard mask, used in access lists, is 0.255.255.255.
How many hosts are in a /8 subnet?
A /8 has 16,777,216 total addresses and 16,777,214 usable hosts (the total minus the network and broadcast addresses, except for /31 and /32).
What is a /8 used for?
Very large network. It is equivalent to 1 class A block (a /8).
How do I calculate a /8 network?
Set the host bits to zero for the network address and to one for the broadcast address. The calculator on this page does it for any /8 block you enter.