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Category Network Utilities

IP Address

Subnet Mask (CIDR)

Adjust Mask Bits: /24

/0/8/16/24/32

Network Address
-

Broadcast Address

First Usable Host

Last Usable Host

Usable Hosts

Wildcard Mask

Subnet Mask

IP Range

Binary Visualization

Possible Subnets (Next Level)

Network	Range	Broadcast

Enter a list of IP addresses (one per line) to find the smallest summarization route (Supernet) that covers them all.

IP List

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About

Subnetting is the practice of dividing a single physical network into multiple smaller logical sub-networks (subnets). This tool provides absolute precision in calculating network parameters, essential for configuring routers, firewalls, and managing IP address allocations efficiently. Unlike basic calculators, this engine handles bitwise operations across the full 32-bit IPv4 space, ensuring accuracy even in edge cases like /31 point-to-point links or /32 host routes.

Proper IP planning prevents address conflicts, optimizes routing table size through summarization (Supernetting), and ensures security boundaries are mathematically enforced. Whether you are designing a Datacenter Leaf-Spine topology or studying for CCNA/CCIE, understanding the binary interaction between the IP Address and the Subnet Mask is non-negotiable.

Formulas

Network calculations rely on bitwise operations between the 32-bit integer representation of the IP address (I) and the Subnet Mask (M).

Network Address:
N = I ∧ M (Bitwise AND)

Broadcast Address:
B = N ∨ ¬M (Network OR Wildcard)

Number of Hosts:
H = 2^{32 − CIDR} − 2 (Subtract Network & Broadcast ID)

Note: For /31 and /32 networks, the − 2 rule does not strictly apply in modern routing contexts (RFC 3021).

Reference Data

CIDR	Subnet Mask	Wildcard Mask	Total IPs	Usable Hosts
/32	255.255.255.255	0.0.0.0	1	1
/31	255.255.255.254	0.0.0.1	2	2 (P2P)
/30	255.255.255.252	0.0.0.3	4	2
/29	255.255.255.248	0.0.0.7	8	6
/28	255.255.255.240	0.0.0.15	16	14
/27	255.255.255.224	0.0.0.31	32	30
/26	255.255.255.192	0.0.0.63	64	62
/25	255.255.255.128	0.0.0.127	128	126
/24	255.255.255.0	0.0.0.255	256	254
/23	255.255.254.0	0.0.1.255	512	510
/22	255.255.252.0	0.0.3.255	1,024	1,022
/21	255.255.248.0	0.0.7.255	2,048	2,046
/20	255.255.240.0	0.0.15.255	4,096	4,094
/16	255.255.0.0	0.0.255.255	65,536	65,534
/8	255.0.0.0	0.255.255.255	16,777,216	16,777,214

Frequently Asked Questions

Traditionally, subnets require a Network ID and Broadcast ID, consuming 2 addresses. However, RFC 3021 enables using /31 subnets for Point-to-Point links, allowing both addresses to be used for hosts, preserving public IP space.

They represent the same data. Subnet Mask is the dot-decimal notation (e.g., 255.255.255.0), while CIDR (Classless Inter-Domain Routing) is the slash notation (e.g., /24) indicating the number of "on" bits in the mask.

Convert all IPs to binary. Align them vertically. Find the longest common sequence of bits from the left. Count these matching bits to get the new CIDR mask. The tool's "Supernet" tab performs this automatically.

Class A: 10.0.0.0/8. Class B: 172.16.0.0/12. Class C: 192.168.0.0/16. These addresses are not routable on the public internet.