CIDR prefix
/17
255.255.128.0
32,766 usable hosts · 32,768 addresses
The mask for /17 is 255.255.128.0 — 32,768 addresses, 32,766 usable hosts. Campus and larger office networks; /22–/23 are common for offices with a few hundred devices.
Mask
255.255.128.0
Wildcard
0.0.127.255
Addresses
32,768
Hosts
32,766
Worked example: 192.168.0.0/17
Network address192.168.0.0/17
Broadcast address192.168.127.255
First host192.168.0.1
Last host192.168.127.254
FAQ — /17
What is the subnet mask for /17?
The subnet mask for /17 is 255.255.128.0 (wildcard: 0.0.127.255). The first 17 bits are the network part, the remaining 15 are the host part.
How many hosts fit in a /17?
A /17 block holds 32,768 addresses, of which 32,766 are usable hosts (the network and broadcast addresses are excluded).
How many /17 subnets fit in a /16?
A /16 network divides into 2 /17 subnets.
What is a /17 used for?
Campus and larger office networks; /22–/23 are common for offices with a few hundred devices.