/6 Subnet Mask ReferenceIPv4
Four /8 networks bundled under mask <code>252.0.0.0</code>: that is a /6, holding 67,108,864 addresses. It dwarfs any conceivable deployment, so the prefix survives mainly in textbooks and route-aggregation worksheets.
/6 facts at a glance
- Subnet mask
- 252.0.0.0
- Wildcard mask
- 3.255.255.255
- Binary mask
- 11111100.00000000.00000000.00000000
- Total addresses
- 67,108,864
- Usable hosts
- 67,108,862 (excludes network & broadcast)
- Block size
- 67,108,864 addresses (226)
- Typical role
- Aggregation and supernetting
Example /6 networks
A /6 spans a large share of the address space, so one aligned example says it all.
| Network | Usable range | Usable hosts |
|---|---|---|
| 196.0.0.0/6 | 196.0.0.1 – 199.255.255.254 | 67,108,862 |
How to calculate a /6 mask
A /6 mask sets the first 6 bits of a 32-bit number to 1 and leaves the remaining 26 bits as 0. In binary that reads 11111100.00000000.00000000.00000000, which converts to dotted decimal 252.0.0.0. Each block covers a contiguous run of 226 = 67,108,864 addresses, and every block starts at a multiple of that size. The wildcard simply flips every bit, giving 3.255.255.255.
Where /6 is used
- Aggregation drills: combining neighboring /8s into one summary line.
- Visualizing the address map, for example 64.0.0.0/6 covering 64.0.0.0 through 67.255.255.255.
- Bit-boundary exercises where the mask stops mid-first-octet.
Alignment rule: a /6 network must start on a first octet divisible by four, such as 64, 68, 124, or 220.
Frequently asked questions
What is the subnet mask for /6?
<code>252.0.0.0</code>, with wildcard <code>3.255.255.255</code>. Six leading one-bits leave 26 host bits.
How many addresses are in a /6?
67,108,864 total; 67,108,862 usable after the standard two-address deduction.
Why would a block this large never be deployed?
Even the largest carriers control only a handful of /8s, and no routing domain approaches tens of millions of hosts. The prefix exists for aggregation math.
Open this block in a calculator
Open the /6 block in the subnet calculator