A /17 is half of a /16, with a mask of 255.255.128.0. The third octet runs 0–127 or 128–255. With 32,766 usable hosts it’s far too big for a single broadcast domain, so networks this size are split into smaller subnets. It’s a common middle step when you summarise or plan an enterprise address space.
Facts
- Prefix
- /17
- Subnet mask
- 255.255.128.0
- Wildcard mask
- 0.0.127.255
- Binary mask
- 11111111.11111111.10000000.00000000
- Total addresses
- 32,768
- Usable hosts
- 32,766
- Example range
- 192.168.0.0/17: 192.168.0.0 – 192.168.127.255
- Typical use
- Large enterprise networks.
Try it
Try: , ,
- CIDR block
- 192.168.0.0/17
- IP range
- 192.168.0.0 – 192.168.127.255
- Addresses
- 32,768
- Usable hosts
- 32,766
- Subnet mask
- 255.255.128.0
- Wildcard mask
- 0.0.127.255
Frequently asked questions
How many hosts are in a /17?
A /17 has 32,768 addresses. Subtracting the network and broadcast addresses leaves 32,766 usable hosts.
What is the subnet mask for /17?
/17 is 255.255.128.0 (wildcard mask 0.0.127.255). In binary that’s 17 ones followed by 15 zeros.