/8 Subnet

A /8 has 16,777,216 addresses, 16,777,214 of them usable by hosts. Its netmask is 255.0.0.0. Enter any address below to see its /8 network.

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Examples:

IPv4 network

16,777,214 usable hosts · 10.0.0.1 to 10.255.255.254

Private (RFC 1918)

Details

Netmask
Wildcard Mask
Broadcast
First Usable
Last Usable
Usable Hosts
Total Addresses
Netmask in Binary

Split Into Subnets

10.0.0.0/910.0.0.0 – 10.127.255.255
10.128.0.0/910.128.0.0 – 10.255.255.255

Subnet Calculator

/8 at a glance

CIDR Prefix/8
Netmask255.0.0.0
Wildcard Mask0.255.255.255
Netmask (Hex)0xFF000000
Total Addresses16,777,216
Usable Hosts16,777,214
Host Bits24
Contains /24s65,536
Binary Mask11111111.00000000.00000000.00000000

A /8 fixes the first 8 bits of the address as the network and leaves 24 bits for hosts, so it holds 2^24 = 16,777,216 addresses. The first is the network address and the last is the broadcast address, leaving 16,777,214 for hosts.

The size of the old Class A networks. 10.0.0.0/8 is the largest private range and is common for big internal networks and VPN address plans.

A /8 can be announced in BGP on its own: /24 is the longest prefix most networks accept.

Other IPv4 Prefixes

/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

IPv6 Prefixes

IPv6 /32IPv6 /36IPv6 /40IPv6 /44IPv6 /48IPv6 /52IPv6 /56IPv6 /60IPv6 /64IPv6 /112IPv6 /126IPv6 /127IPv6 /128

Questions

How many usable IP addresses are in a /8?
16,777,214. A /8 has 16,777,216 addresses; the network and broadcast addresses are not usable by hosts.
What is the subnet mask for /8?
255.0.0.0. The wildcard (inverse) mask, used in Cisco ACLs, is 0.255.255.255.
How many /24 networks are in a /8?
65,536. Each step from /8 to /24 doubles the number of networks.
Is 255.0.0.0 the same as /8?
Yes. 255.0.0.0 written in binary is 8 ones followed by 24 zeros, which is what /8 means.

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