How many IP addresses are in a /24 subnet?

A /24 subnet contains 256 total IP addresses (2^8 = 256). Two are reserved: the network address (first IP) and the broadcast address (last IP), leaving 254 usable host addresses. The subnet mask for a /24 is 255.255.255.0.

What are the private IP address ranges?

RFC 1918 defines three private IPv4 ranges that are not routable on the public internet: 10.0.0.0/8 (Class A, ~16.7 million addresses), 172.16.0.0/12 (Class B, ~1 million addresses, covers 172.16.x.x through 172.31.x.x), and 192.168.0.0/16 (Class C, 65,536 addresses, used in most home networks).

How do I calculate network address from a CIDR block?

The network address is found by performing a bitwise AND between the IP address and the subnet mask. For 192.168.1.100/24: the subnet mask is 255.255.255.0, and 192.168.1.100 AND 255.255.255.0 = 192.168.1.0. The network address is always the first IP in the block. Use this calculator to compute it instantly for any CIDR block.

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Subnet Reference

Every prefix /0–/32: host counts, subnet masks, use cases.

/8 /16 /24 /28 /30 /32

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Popular Ranges

192.168.1.0/24 RFC 1918

Second most common home router subnet

192.168.0.0/24 RFC 1918

Most common home router default subnet

10.0.0.0/8 RFC 1918

10/8 — the largest private block

10.0.0.0/16 RFC 1918

Popular AWS VPC starting block

172.16.0.0/12 RFC 1918

172.16–31.x.x — mid-size private block

172.31.0.0/16 RFC 1918

AWS default VPC block in new accounts

192.168.0.0/16 RFC 1918

192.168.x.x — the home/office standard

127.0.0.0/8 Special

Localhost — the loopback block

0.0.0.0/0 Special

The catch-all route for all traffic

169.254.0.0/16 Special

Auto-assigned when DHCP fails

100.64.0.0/10 Special

Shared address space for ISP NAT

224.0.0.0/4 Special

Multicast group addresses

What is CIDR notation?

CIDR (Classless Inter-Domain Routing) notation describes a block of IP addresses using a base address and a prefix length. For example, 192.168.1.0/24 means:

→The network starts at 192.168.1.0
→The /24 means the first 24 bits are fixed (the network portion)
→The remaining 8 bits are free — giving 256 total addresses (254 usable)

Read the full guide → What Is CIDR Notation?

Quick Prefix Reference

Prefix	Subnet Mask	Usable Hosts
/8	255.0.0.0	16,777,214
/16	255.255.0.0	65,534
/24	255.255.255.0	254
/25	255.255.255.128	126
/26	255.255.255.192	62
/27	255.255.255.224	30
/28	255.255.255.240	14
/30	255.255.255.252	2
/32	255.255.255.255	1

View full /0–/32 reference table →

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