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/3 subnet — netmask 224.0.0.0

A /3 has 536,870,912 addresses and 536,870,910 usable hosts.

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IPv4 address with prefix

Network
Broadcast
Netmask
Wildcard (ACL)
First usable host
Last usable host
Total addresses
Usable hosts
Binary mask
Address type

/3 at a glance

Netmask	`224.0.0.0`
Wildcard mask	`31.255.255.255`
Binary	`11100000.00000000.00000000.00000000`
Total addresses	536,870,912
Usable hosts	536,870,910

Cloud note: AWS reserves 5 addresses in every VPC subnet, and Azure reserves 5 too, so usable hosts in a cloud subnet are total − 5.

CIDR prefix table

Prefix	Netmask	Addresses
/8	`255.0.0.0`	16,777,216
/12	`255.240.0.0`	1,048,576
/16	`255.255.0.0`	65,536
/20	`255.255.240.0`	4,096
/22	`255.255.252.0`	1,024
/23	`255.255.254.0`	512
/24	`255.255.255.0`	256
/25	`255.255.255.128`	128
/26	`255.255.255.192`	64
/27	`255.255.255.224`	32
/28	`255.255.255.240`	16
/29	`255.255.255.248`	8
/30	`255.255.255.252`	4
/31	`255.255.255.254`	2
/32	`255.255.255.255`	1

Private ranges (RFC 1918)

10.0.0.0/8 — 16.7 million addresses
172.16.0.0/12 — 1 million addresses
192.168.0.0/16 — 65,536 addresses
100.64.0.0/10 — carrier-grade NAT (RFC 6598), also used by Tailscale