SubnetPad

/8 Subnet Calculator

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A /8 block (historically "Class A") contains 16,777,216 addresses. Three /8 blocks are reserved for private networking (RFC 1918), and the rest are allocated to large organizations and ISPs.

/1
/32

/8 = mask 255.0.0.0 • 16,777,214 usable addresses

Results for 10.0.0.0/8

Private (RFC 1918)Class A
Network addressThe first address — identifies the subnet itself
Broadcast addressThe last address — used to reach every device at once
Subnet maskSame as /8 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 hosts16,777,216 total addresses in this subnet
More detailsNeighboring subnets, wildcard mask, hex, reverse DNS, and binary breakdown

Neighboring /8 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 address00001010.00000000.00000000.00000000
Subnet mask11111111.00000000.00000000.00000000
Network00001010.00000000.00000000.00000000
Broadcast00001010.11111111.11111111.11111111

Quick facts for /8

/8 reference guideBit split, overview, sizing tables, notable networks, and FAQ

Binary bit split

Network bits (8)Host bits (24)
Network bits
8
Host bits
24
Subnet mask
255.0.0.0
Wildcard mask
0.255.255.255
Total addresses
16,777,216
Usable hosts
16,777,214
Hosts formula
2^24 − 2
/24 relationship
65,536 × /24 networks

Overview

A /8 block (historically "Class A") contains 16,777,216 addresses. Three /8 blocks are reserved for private networking (RFC 1918), and the rest are allocated to large organizations and ISPs.

Common use cases

  • Large enterprise private networks (10.0.0.0/8)
  • Major ISP address allocations
  • Cloud provider backbone networks
  • Military and government networks

Subnet sizing reference

Divide /8 into…

PrefixSubnetsHosts each
/928,388,606
/1044,194,302
/1182,097,150
/12161,048,574

/8 fits inside…

SupernetHosts/8s inside
/733,554,4302
/667,108,8624
/5134,217,7268
/4268,435,45416

Notable /8 networks

  • 10.0.0.0/8RFC 1918 Class A private range
  • 127.0.0.0/8Loopback addresses
  • 100.64.0.0/10Carrier-Grade NAT (CGNAT)

Frequently asked questions

Common questions about /8 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