IP Subnet Calculator - IPv4 & IPv6 CIDR / Netmask
Professional IP subnet calculator for network engineers and sysadmins. Calculate CIDR prefix /0 to /32, subnet masks, wildcard masks, usable host ranges, binary representations, classful ranges, and IPv6 /64 prefix delegations.
IPv4 Network Parameters
192.168.1.0 /24
Network Architecture & Subnetting Guide: IP Subnet Calculator - IPv4 & IPv6 CIDR / Netmask
The IP Subnet Calculator - IPv4 & IPv6 CIDR / Netmask provides exact bitmask calculations, CIDR notation analysis, and usable IP address allocations for network engineers and system administrators.
CIDR Subnetting & Address Allocation Rules
IP subnetting divides larger networks into smaller, isolated routing domains to optimize traffic flow and bolster network security. Each subnet is defined by its 32-bit (IPv4) or 128-bit (IPv6) prefix mask.
Our calculator computes network IDs, first/last usable host addresses, and broadcast boundaries instantly with full 32-bit binary representations.
Step-by-Step Instructions
Enter IPv4 Address & Subnet Mask
Input any IPv4 IP address (e.g. `192.168.1.100`, `10.0.0.1`) and select a CIDR prefix length (e.g. `/24`, `/28`, `/16`) or dotted decimal mask (e.g. `255.255.255.0`).
Execute Binary Bitwise Subnetting
The calculator performs bitwise AND operations (`IP & Mask`) to identify network boundaries in real time.
Inspect Network Addressing Range
Review calculated Network Address, Broadcast Address, First Usable Host IP, Last Usable Host IP, and Total Usable Hosts.
Explore Binary Subnet Masks & Wildcards
Review 32-bit binary representations, Cisco Wildcard Mask (inverse mask), and standard IPv4 class (Class A, B, C, Private/Public status).
Key Features & Capabilities
- Full IPv4 Classless Inter-Domain Routing (CIDR) calculation from `/0` to `/32`
- Network parameters: Network ID, Broadcast IP, First Usable Host, Last Usable Host, Total Hosts (`2^n`), and Usable Hosts (`2^n - 2`)
- 32-bit binary breakdown highlighting Network Bits vs Host Bits with visual subnet boundary markers
- Cisco Access Control List (ACL) Wildcard Mask calculation (`255.255.255.255 - Subnet Mask`)
- IPv4 Address Classification: RFC 1918 Private ranges (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), Loopback, APIPA (169.254.0.0/16), and Multicast
- Instant client-side networking calculation with zero server latency
Frequently Asked Questions
How do you calculate the network address and usable host range from a CIDR notation like 192.168.1.50/26?
A `/26` subnet mask has 26 network bits and 6 host bits (`32 - 26 = 6 host bits`). The subnet mask is `255.255.255.192`. Total IP addresses per subnet = `2^6 = 64`. For `192.168.1.50`, the block spans `192.168.1.0` to `192.168.1.63`. Network Address is `192.168.1.0`, Broadcast Address is `192.168.1.63`, and the Usable Host Range is `192.168.1.1` through `192.168.1.62` (62 usable hosts).
Why are 2 addresses subtracted from the total number of hosts in a subnet (2^n - 2)?
In standard IPv4 subnets, the very first address (all host bits set to 0) is reserved as the Network Identifier, and the very last address (all host bits set to 1) is reserved as the Directed Broadcast Address. Therefore, usable hosts = `2^n - 2` (except on point-to-point `/31` links under RFC 3021).
What is a Cisco Wildcard Mask and how is it calculated?
A Wildcard Mask is the bitwise inverse of a subnet mask used in Cisco router Access Control Lists (ACLs) and OSPF routing. It is calculated by subtracting each octet of the subnet mask from 255 (e.g. for mask `255.255.255.0`, the wildcard mask is `0.0.0.255`).
What are the RFC 1918 Private IP Address ranges?
RFC 1918 defines three non-routable private IP address ranges for local networks: **Class A:** `10.0.0.0` to `10.255.255.255` (`10.0.0.0/8`), **Class B:** `172.16.0.0` to `172.31.255.255` (`172.16.0.0/12`), and **Class C:** `192.168.0.0` to `192.168.255.255` (`192.168.0.0/16`).
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