# /10 Subnet Mask (255.192.0.0) – Hosts, Range & FAQ

> The /10 subnet mask is 255.192.0.0. A /10 block holds 4,194,304 addresses with 4,194,302 usable hosts — ranges, wildcard, binary math and FAQs.

- Page URL: https://itinsighthub.com/subnet/10/
- Markdown variant of this page: append `?format=md` to any URL on this site or send `Accept: text/markdown`.
- Full site index for AI assistants: https://itinsighthub.com/llms.txt
- Full site export: https://itinsighthub.com/llms-full.txt

# /10 Subnet Mask ReferenceIPv4

A /10 quarters a /8, giving 4,194,304 addresses behind mask 255.192.0.0. One particular /10 is a celebrity: 100.64.0.0/10, the carrier-grade NAT range on which much of the world's mobile and broadband traffic begins life.

The /10 subnet mask is 255.192.0.0, equivalent to 0.63.255.255 as a wildcard. A /10 block contains 4,194,304 IP addresses (4,194,302 usable hosts).

## /10 facts at a glance

- **Subnet mask:** 255.192.0.0
- **Wildcard mask:** 0.63.255.255
- **Binary mask:** 11111111.11000000.00000000.00000000
- **Total addresses:** 4,194,304
- **Usable hosts:** 4,194,302 (excludes network & broadcast)
- **Block size:** 4,194,304 addresses (222)
- **Typical role:** Large enterprise and carrier aggregation

## Example /10 networks

Three consecutive /10 blocks, starting at the /10 boundary that contains 198.51.100.0:

| Network | Usable range | Usable hosts |
| --- | --- | --- |
| 198.0.0.0/10 | 198.0.0.1 – 198.63.255.254 | 4,194,302 |
| 198.64.0.0/10 | 198.64.0.1 – 198.127.255.254 | 4,194,302 |
| 198.128.0.0/10 | 198.128.0.1 – 198.191.255.254 | 4,194,302 |

## How to calculate a /10 mask

A /10 mask sets the first 10 bits of a 32-bit number to 1 and leaves the remaining 22 bits as 0. In binary that reads `11111111.11000000.00000000.00000000`, which converts to dotted decimal `255.192.0.0`. Each block covers a contiguous run of 222 = 4,194,304 addresses, and every block starts at a multiple of that size. The wildcard simply flips every bit, giving `0.63.255.255`.

## Where /10 is used

- Carrier-grade NAT subscriber addressing (RFC 6598 shared address space).
- Consumer mesh and VPN products that deliberately pick the 100.64.0.0/10 region to avoid clashing with RFC 1918 home ranges.
- Large internal segmentation where a /8 is excessive but a /11 feels tight.

RFC 6598 assigns 100.64.0.0/10, running 100.64.0.0 through 100.127.255.255, to carrier-grade NAT. Thousands of subscribers share these addresses, so they must stay off the public Internet and out of enterprise addressing plans.

## Frequently asked questions

**What is 100.64.0.0/10?**

Shared address space for carrier-grade NAT, standardized in RFC 6598. ISPs translate subscriber traffic from these addresses onto public IPs at the network edge.

**What is the subnet mask for a /10?**

255.192.0.0, wildcard 0.63.255.255: ten fixed bits and twenty-two host bits.

**How many addresses are in a /10?**

4,194,304 total and 4,194,302 usable by convention.

**Should I use 100.64.x.x addresses inside my company?**

Best avoided. Standards reserve the range for ISP CGNAT, and remote users behind mobile carriers already source traffic from it, which invites confusing overlaps.

## Open this block in a calculator

[Open the /10 block in the subnet calculator](https://itinsighthub.com/subnet-calculator/?q=198.0.0.0%2F10)

[Get the /10 wildcard mask →](https://itinsighthub.com/wildcard-mask-calculator/?q=%2F10)

### Related prefixes

[/9](https://itinsighthub.com/subnet/9/)[/11](https://itinsighthub.com/subnet/11/)[/24](https://itinsighthub.com/subnet/24/)[/26](https://itinsighthub.com/subnet/26/)[/28](https://itinsighthub.com/subnet/28/)[/30](https://itinsighthub.com/subnet/30/)

← /9 subnet mask
/11 subnet mask →

---

© 2026 ITInsightHub · [About](https://itinsighthub.com/about/) · [Contact](https://itinsighthub.com/contact/) · [Privacy](https://itinsighthub.com/privacy/)