Subnet Calculator

Calculate subnet masks, CIDR notation, usable IP ranges, and network details instantly.

CIDR Notation IP Ranges Network Details

CIDR Quick Reference

Common CIDR prefix sizes and their host counts

CIDR	Subnet Mask	Total IPs	Usable Hosts
/8	255.0.0.0	16,777,216	16,777,214
/16	255.255.0.0	65,536	65,534
/24	255.255.255.0	256	254
/27	255.255.255.224	32	30
/28	255.255.255.240	16	14
/30	255.255.255.252	4	2
/32	255.255.255.255	1	Single host

Understanding Subnetting

Learn the basics of IP networking, subnetting, and addressing to better manage your networks.

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What is Subnetting?

Subnetting is the practice of dividing a network into two or more smaller networks. It helps improve network performance and security by reducing broadcast traffic and organizing hosts into logical groups.

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Understanding CIDR

Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and routing. It uses a suffix (e.g., /24) to indicate the number of bits used for the network prefix, replacing the older class-based system.

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Private vs Public IPs

Private IP addresses (RFC 1918) are used within local networks and are not routable on the internet. Public IP addresses are assigned by ISPs and are unique across the entire internet.

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IPv4 vs IPv6

IPv4 uses 32-bit addresses (approx 4.3 billion addresses), while IPv6 uses 128-bit addresses (virtually infinite). IPv6 was developed to solve the IPv4 address exhaustion problem.

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Subnet Masks

A subnet mask is a 32-bit number that masks an IP address and divides it into network address and host address. It distinguishes the network portion from the host portion of an IP address.

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Broadcast Address

The last address in a subnet is reserved as the broadcast address. It allows sending data to all devices on that specific subnet simultaneously. It cannot be assigned to a specific host.

Frequently Asked Questions

What is a subnet? expand_more

A subnet divides a larger network into smaller segments. Each subnet has its own range of IP addresses, defined by a network address and subnet mask.

What is CIDR notation? expand_more

CIDR notation like /24 specifies how many bits of the IP address are the network portion. /24 means the first 24 bits, leaving 8 bits for 256 addresses.

How many usable hosts does a /24 subnet have? expand_more

A /24 subnet has 256 total addresses. Subtract 2 for the network and broadcast addresses, leaving 254 usable host addresses.

What is the difference between subnet mask and wildcard mask? expand_more

They are binary inverses. A /24 subnet mask is 255.255.255.0 and its wildcard mask is 0.0.0.255. Wildcard masks are used in ACLs and OSPF configuration.

Can I subnet IPv6 addresses? expand_more

Yes. IPv6 subnetting works the same way using CIDR notation. A common allocation is /48 per organization, subnetted into /64 networks for individual LANs.

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