Visual CIDR Subnet Calculator – IPv4 / IPv6 Subnetting & Supernetting Planner

Calculate IPv4 and IPv6 subnets with interactive 32-bit binary mask visualizer. Plan VPC cloud networks, calculate usable host IP ranges, wildcard masks, and sub-divisions.

IP Address / CIDR Prefix

Prefix Mask: /24

VPC Presets:

Interactive 32-Bit Binary Visualizer ■ Network Bits • ■ Host Bits (Click bit to resize CIDR)

Network Address

192.168.1.0

Subnet Mask & Wildcard

255.255.255.0

Wildcard: 0.0.0.255

Broadcast Address

192.168.1.255

Usable Host Range

192.168.1.1 – 192.168.1.254

Host Capacities

254 usable hosts

256 total IPs

Routing Scope & Class

RFC 1918 Private

Class C Network

Subnet Subdivision Planning (/4 Equal Slices)

Subnet	CIDR Block	Usable Host Range	Broadcast	Usable Hosts

Terraform AWS VPC Resource

Understanding CIDR Notation & IPv4 Subnetting

Classless Inter-Domain Routing (CIDR) is the standard method used across cloud infrastructure (AWS VPC, Google Cloud, Azure Virtual Networks) and enterprise networking to allocate IP addresses and specify routing prefixes without rigid legacy Class A/B/C boundaries.

How Subnetting Works

Every IPv4 address contains 32 bits, divided into two distinct sections: the Network Prefix and the Host Identifier. The suffix (e.g. /24) denotes how many leading bits belong to the network:

Network Address: The very first IP in the block (all host bits set to 0). Identifies the subnet itself and cannot be assigned to individual machines.
Broadcast Address: The final IP in the block (all host bits set to 1). Transmits packets to all hosts across the local broadcast domain.
Usable Hosts: Equal to 2^{(32 − CIDR)} − 2. For example, a /24 network provides 256 total IP addresses and 254 assignable host addresses.

Cloud VPC Architecture Best Practices

When architecting a production Virtual Private Cloud (VPC), starting with a /16 block (e.g., 10.0.0.0/16 with 65,534 IPs) allows carving out dedicated /24 subnets for public ingress load balancers, private application tiers, and isolated database clusters across multiple Availability Zones.

Frequently asked questions

Why are two IP addresses subtracted from every subnet?

In standard IPv4 networking, the first address is reserved as the Network Identifier, and the last address is reserved as the Subnet Broadcast. (Note: AWS VPC reserves 5 IP addresses per subnet for internal DNS and routers).

What are RFC 1918 private IP ranges?

RFC 1918 defines three private blocks that are never routed on the public internet: 10.0.0.0/8 (10.0.0.0 – 10.255.255.255), 172.16.0.0/12 (172.16.0.0 – 172.31.255.255), and 192.168.0.0/16 (192.168.0.0 – 192.168.255.255).

What is a wildcard mask?

A wildcard mask is the exact inverted binary complement of a subnet mask (e.g. Subnet Mask 255.255.255.0 = Wildcard 0.0.0.255). It is extensively used in Cisco ACLs and OSPF routing configurations.

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