What does a /32 CIDR represent?

A /32 subnet represents a single specific host address (Host route / loopback). There are no separate network or broadcast addresses, yielding exactly 1 usable address.

Are subnet calculations performed locally?

Yes. All calculations (bitwise AND/OR operations, mask derivations, host ranges) run 100% locally in your browser with zero latency and zero data transfer.

How do I calculate subnets for point-to-point links?

Use /30 for traditional legacy equipment (2 usable hosts, 1 net, 1 broadcast) or /31 (RFC 3021) for modern Cisco, Juniper, and Linux point-to-point router links where both addresses are usable.

What is the relationship between a Subnet Mask and a Wildcard Mask?

A wildcard mask is the exact bitwise inversion of a subnet mask (255.255.255.255 minus the subnet mask). For example, a /24 subnet mask of 255.255.255.0 corresponds to a wildcard mask of 0.0.0.255, which is frequently used in Cisco ACLs and OSPF network statements.

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IPv4 Subnet Calculator & CIDR Tool

Calculate subnet masks, wildcard masks, network and broadcast addresses, usable host ranges, and 32-bit binary representations instantly without external API dependencies.

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Subnetting & CIDR Guide

Understanding IPv4 Subnetting & CIDR Math

Subnetting divides a larger network into smaller, more efficient logical segments. Classless Inter-Domain Routing (CIDR) uses variable-length prefix masks (e.g. /24) to allocate address blocks flexibly without the rigidity of legacy Class A, B, and C boundaries.

Network vs Broadcast Addresses

The Network Address (all host bits 0) identifies the subnet itself. The Broadcast Address (all host bits 1) reaches all hosts on the subnet. Because both are reserved, usable hosts equal 2^(32 - CIDR) - 2.

Wildcard Mask Inversion

The inverse of the subnet mask (e.g. 0.0.0.255 for a 255.255.255.0 mask) determines which bits to inspect in Cisco ACLs, route maps, and OSPF network statements.

RFC 3021 /31 Subnets

Modern point-to-point router links utilize /31 subnets where both IP addresses serve as host interfaces without wasting two IPs on network and broadcast designations.

IPv4 CIDR Prefix & Subnet Mask Cheat Sheet (/24 to /32)

Standard engineering reference table for IPv4 Classless Inter-Domain Routing (CIDR) prefixes, dotted decimal subnet masks, wildcard masks, and usable host capacities.

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CIDR	Subnet Mask	Wildcard Mask	Total IPs	Usable Hosts	Typical Architecture
/24	255.255.255.0	0.0.0.255	256	254	Standard Class C / Corporate VLAN
/25	255.255.255.128	0.0.0.127	128	126	Half Class C / Department subnet
/26	255.255.255.192	0.0.0.63	64	62	Quarter Class C / Server cluster
/27	255.255.255.224	0.0.0.31	32	30	Medium branch office or staging zone
/28	255.255.255.240	0.0.0.15	16	14	Small subnet, DMZ or database rack
/29	255.255.255.248	0.0.0.7	8	6	Public IP gateway / HA firewall cluster
/30	255.255.255.252	0.0.0.3	4	2	Traditional point-to-point link
/31	255.255.255.254	0.0.0.1	2	2	RFC 3021 Modern P2P router link
/32	255.255.255.255	0.0.0.0	1	1	Single Host route / Loopback interface

Frequently Asked Questions

Common questions regarding CIDR subnet calculations and host capacities.

In standard subnets (/1 to /30), the first address is reserved as the network identifier and the final address is reserved as the all-hosts broadcast address. Thus, 2 addresses are subtracted from the total capacity.