/11 Subnet Mask ReferenceIPv4
Eight equal wedges tile a /8, and each wedge is a /11: mask <code>255.224.0.0</code>, 2,097,152 addresses. Architects reach for one when they want a generous internal region without committing a full /10.
/11 facts at a glance
- Subnet mask
- 255.224.0.0
- Wildcard mask
- 0.31.255.255
- Binary mask
- 11111111.11100000.00000000.00000000
- Total addresses
- 2,097,152
- Usable hosts
- 2,097,150 (excludes network & broadcast)
- Block size
- 2,097,152 addresses (221)
- Typical role
- Large enterprise and carrier aggregation
Example /11 networks
Three consecutive /11 blocks, starting at the /11 boundary that contains 198.51.100.0:
| Network | Usable range | Usable hosts |
|---|---|---|
| 198.32.0.0/11 | 198.32.0.1 – 198.63.255.254 | 2,097,150 |
| 198.64.0.0/11 | 198.64.0.1 – 198.95.255.254 | 2,097,150 |
| 198.96.0.0/11 | 198.96.0.1 – 198.127.255.254 | 2,097,150 |
How to calculate a /11 mask
A /11 mask sets the first 11 bits of a 32-bit number to 1 and leaves the remaining 21 bits as 0. In binary that reads 11111111.11100000.00000000.00000000, which converts to dotted decimal 255.224.0.0. Each block covers a contiguous run of 221 = 2,097,152 addresses, and every block starts at a multiple of that size. The wildcard simply flips every bit, giving 0.31.255.255.
Where /11 is used
- Dividing a corporate /8 among data centers, regions, or subsidiaries.
- Summary lines in design documents that keep high-level maps readable.
- Lab topologies sized between the familiar /10 and /12 landmarks.
Handy landmark: the RFC 1918 private block <code>172.16.0.0/12</code> occupies exactly the upper half of <code>172.0.0.0/11</code>, which spans 172.0.0.0 through 172.31.255.255.
Frequently asked questions
What is the subnet mask for /11?
<code>255.224.0.0</code>, wildcard <code>0.31.255.255</code>. Eleven fixed bits means the second octet advances in steps of 32.
How many addresses are in a /11?
2,097,152 total; 2,097,150 usable after the standard deduction.
How many /11s fit in a /8?
Eight. Their networks begin at second-octet values 0, 32, 64, 96, 128, 160, 192, and 224.
Open this block in a calculator
Open the /11 block in the subnet calculator