CIDR prefix
/9
255.128.0.0
8,388,606 usable hosts · 8,388,608 addresses
The mask for /9 is 255.128.0.0 — 8,388,608 addresses, 8,388,606 usable hosts. Large enterprise and carrier networks.
Mask
255.128.0.0
Wildcard
0.127.255.255
Addresses
8,388,608
Hosts
8,388,606
Worked example: 10.0.0.0/9
Network address10.0.0.0/9
Broadcast address10.127.255.255
First host10.0.0.1
Last host10.127.255.254
FAQ — /9
What is the subnet mask for /9?
The subnet mask for /9 is 255.128.0.0 (wildcard: 0.127.255.255). The first 9 bits are the network part, the remaining 23 are the host part.
How many hosts fit in a /9?
A /9 block holds 8,388,608 addresses, of which 8,388,606 are usable hosts (the network and broadcast addresses are excluded).
How many /9 subnets fit in a /8?
A /8 network divides into 2 /9 subnets.
What is a /9 used for?
Large enterprise and carrier networks.