SubnetPad

/17 Subnet Calculator

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A /17 block contains 32,768 addresses with 32,766 usable. Useful for splitting a /16 into two equal halves, such as dividing a VPC into public and private halves.

/1
/32

/17 = mask 255.255.128.0 • 32,766 usable addresses

Results for 192.168.0.0/17

Private (RFC 1918)Class C
Network addressThe first address — identifies the subnet itself
Broadcast addressThe last address — used to reach every device at once
Subnet maskSame as /17 in CIDR notation
First usable hostThe first IP you can assign to a device
Last usable hostThe last IP you can assign to a device
Usable hosts32,768 total addresses in this subnet
More detailsNeighboring subnets, wildcard mask, hex, reverse DNS, and binary breakdown

Neighboring /17 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 address11000000.10101000.00000000.00000000
Subnet mask11111111.11111111.10000000.00000000
Network11000000.10101000.00000000.00000000
Broadcast11000000.10101000.01111111.11111111

Quick facts for /17

/17 reference guideBit split, overview, sizing tables, notable networks, and FAQ

Binary bit split

Network bits (17)Host bits (15)
Network bits
17
Host bits
15
Subnet mask
255.255.128.0
Wildcard mask
0.0.127.255
Total addresses
32,768
Usable hosts
32,766
Hosts formula
2^15 − 2
/24 relationship
128 × /24 networks

Overview

A /17 block contains 32,768 addresses with 32,766 usable. Useful for splitting a /16 into two equal halves, such as dividing a VPC into public and private halves.

Common use cases

  • Split a /16 VPC into public and private halves
  • Medium enterprise network allocation
  • ISP customer aggregate blocks

Subnet sizing reference

Divide /17 into…

PrefixSubnetsHosts each
/18216,382
/1948,190
/2084,094
/21162,046

/17 fits inside…

SupernetHosts/17s inside
/1665,5342
/15131,0704
/14262,1428
/13524,28616

Notable /17 networks

  • 192.168.0.0/17Lower half of 192.168.x.x range
  • 192.168.128.0/17Upper half of 192.168.x.x range

Frequently asked questions

Common questions about /17 networks, subnet masks, and use cases.

All CIDR prefix sizes

/0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32