More detailsNeighboring subnets, wildcard mask, hex, reverse DNS, and binary breakdown
Neighboring /9 subnets
- Wildcard mask
- Used in Cisco ACLs and OSPF
- CIDR notation
- IP in hexadecimal
- IP as 32-bit integer
- Reverse DNS (PTR)
- Host bits / subnet bits
Binary breakdown
IP address
00001010.00000000.00000000.00000000Subnet mask
11111111.10000000.00000000.00000000Network
00001010.00000000.00000000.00000000Broadcast
00001010.01111111.11111111.11111111Quick facts for /9
- Subnet mask: 255.128.0.0
- Wildcard: 0.127.255.255
- Usable hosts: 8,388,606
- Total addresses: 8,388,608
/9 reference guideBit split, overview, sizing tables, notable networks, and FAQ
Binary bit split
11111111·10000000·00000000·00000000
Network bits (9)Host bits (23)
- Network bits
- 9
- Host bits
- 23
- Subnet mask
- 255.128.0.0
- Wildcard mask
- 0.127.255.255
- Total addresses
- 8,388,608
- Usable hosts
- 8,388,606
- Hosts formula
- 2^23 − 2
- /24 relationship
- 32,768 × /24 networks
Overview
A /9 block contains 8,388,608 addresses. Common in large enterprise networks where the full 10.0.0.0/8 space is split in two.
Common use cases
- Large enterprise address space divided from a /8
- Major cloud availability zone addressing
- ISP customer allocation pools
Subnet sizing reference
Notable /9 networks
10.0.0.0/9Lower half of 10.x.x.x private range10.128.0.0/9Upper half of 10.x.x.x private range
Frequently asked questions
Common questions about /9 networks, subnet masks, and use cases.