# /8 Subnet Mask (255.0.0.0) – Hosts, Range & FAQ

> The /8 subnet mask is 255.0.0.0. A /8 block holds 16,777,216 addresses with 16,777,214 usable hosts — ranges, wildcard, binary math and FAQs.

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# /8 Subnet Mask ReferenceIPv4

One fixed byte, three free: a /8 holds 16,777,216 addresses and echoes the Class A era when a single organization owned an entire first octet. Whole public /8s are scarce now, but two of them touch every engineer daily: 10.0.0.0/8 for private networks and 127.0.0.0/8 for loopback.

The /8 subnet mask is 255.0.0.0, equivalent to 0.255.255.255 as a wildcard. A /8 block contains 16,777,216 IP addresses (16,777,214 usable hosts).

## /8 facts at a glance

- **Subnet mask:** 255.0.0.0
- **Wildcard mask:** 0.255.255.255
- **Binary mask:** 11111111.00000000.00000000.00000000
- **Total addresses:** 16,777,216
- **Usable hosts:** 16,777,214 (excludes network & broadcast)
- **Block size:** 16,777,216 addresses (224)
- **Typical role:** Legacy Class A equivalent

## Example /8 networks

A /8 spans a large share of the address space, so one aligned example says it all.

| Network | Usable range | Usable hosts |
| --- | --- | --- |
| 198.0.0.0/8 | 198.0.0.1 – 198.255.255.254 | 16,777,214 |

## How to calculate a /8 mask

A /8 mask sets the first 8 bits of a 32-bit number to 1 and leaves the remaining 24 bits as 0. In binary that reads `11111111.00000000.00000000.00000000`, which converts to dotted decimal `255.0.0.0`. Each block covers a contiguous run of 224 = 16,777,216 addresses, and every block starts at a multiple of that size. The wildcard simply flips every bit, giving `0.255.255.255`.

## Where /8 is used

- Private enterprise addressing: RFC 1918's 10.0.0.0/8 is the default canvas for large internal networks.
- Loopback testing: any 127.x.x.x address loops back to the local machine (RFC 1122).
- Summarization roots for hyperscale operators whose internal maps are drawn in /8 strokes.
- Legacy public allocations from the classful period, still visible in whois records.

RFC 1918 reserves 10.0.0.0/8 for private internets: freely reusable behind NAT, but such packets must never surface on the public Internet.

History lesson: classful addressing handed out first octets 1 through 126 as indivisible /8s, leaving barely more than a hundred public blocks for the whole world. That shortage is precisely what CIDR was invented to fix.

One /8 subdivides into 256 /16s or 65,536 /24s, which keeps it useful as a top-down planning unit even when only fragments get allocated.

## Frequently asked questions

**How many hosts are in a /8?**

16,777,214 usable of 16,777,216 total addresses. Two are withheld: the lowest names the network and the highest serves as the broadcast address.

**What is the subnet mask for a /8?**

255.0.0.0, with wildcard 0.255.255.255. Only the first octet identifies the network; the rest belongs to hosts.

**Why is 10.0.0.0/8 so popular internally?**

It is the largest RFC 1918 pool, over 16.7 million private addresses, easy to remember and easy to subnet hierarchically, and guaranteed never to collide with public routing.

**Is 127.0.0.1 part of a /8?**

Yes. The entire 127.0.0.0/8 block is loopback under RFC 1122; 127.0.0.1 is merely its best-known member, and every other 127.x.x.x address behaves identically.

## Open this block in a calculator

[Open the /8 block in the subnet calculator](https://itinsighthub.com/subnet-calculator/?q=198.0.0.0%2F8)

[Get the /8 wildcard mask →](https://itinsighthub.com/wildcard-mask-calculator/?q=%2F8)

### Related prefixes

[/7](https://itinsighthub.com/subnet/7/)[/9](https://itinsighthub.com/subnet/9/)[/24](https://itinsighthub.com/subnet/24/)[/26](https://itinsighthub.com/subnet/26/)[/28](https://itinsighthub.com/subnet/28/)[/30](https://itinsighthub.com/subnet/30/)

← /7 subnet mask
/9 subnet mask →

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