IP Subnet Calculator Tool

IP Version

IPv4 IPv6

IP Address

Subnet Mask / Prefix Length

Calculation Type

Recent Calculations

Example Subnet Calculations & Network Scenarios

Explore these practical network configurations used in real-world environments:

192.168.1.0/24
Home/SOHO Network

10.0.0.0/8
Enterprise Core

172.16.0.0/16
Campus Network

203.0.113.0/29
DMZ Segment

2001:db8::/64
IPv6 LAN Segment

192.168.0.0/30
WAN Link

10.10.10.0/27
Server Farm

172.20.1.0/25
WiFi Network

198.51.100.0/26
Web Hosting

Complete IPv4 CIDR Reference Table

Comprehensive reference for all IPv4 subnet sizes with network planning information:

CIDR	Subnet Mask	Wildcard Mask	Total IPs	Usable Hosts	Subnets in Class C	Network Use Case
/32	255.255.255.255	0.0.0.0	1	0	256	Host route/Loopback
/31	255.255.255.254	0.0.0.1	2	2*	128	Point-to-point (RFC 3021)
/30	255.255.255.252	0.0.0.3	4	2	64	Point-to-point links
/29	255.255.255.248	0.0.0.7	8	6	32	Small office/branch
/28	255.255.255.240	0.0.0.15	16	14	16	Department subnet
/27	255.255.255.224	0.0.0.31	32	30	8	Small LAN/Server farm
/26	255.255.255.192	0.0.0.63	64	62	4	Medium office LAN
/25	255.255.255.128	0.0.0.127	128	126	2	Large office/WiFi
/24	255.255.255.0	0.0.0.255	256	254	1	Standard LAN
/23	255.255.254.0	0.0.1.255	512	510	1/2	Large LAN
/22	255.255.252.0	0.0.3.255	1,024	1,022	1/4	Very large LAN
/21	255.255.248.0	0.0.7.255	2,048	2,046	1/8	Small enterprise
/20	255.255.240.0	0.0.15.255	4,096	4,094	1/16	Medium enterprise
/19	255.255.224.0	0.0.31.255	8,192	8,190	1/32	Large enterprise
/18	255.255.192.0	0.0.63.255	16,384	16,382	1/64	ISP allocation
/17	255.255.128.0	0.0.127.255	32,768	32,766	1/128	Large ISP block
/16	255.255.0.0	0.0.255.255	65,536	65,534	1/256	Class B network
/15	255.254.0.0	0.1.255.255	131,072	131,070	1/512	Large organization
/14	255.252.0.0	0.3.255.255	262,144	262,142	1/1024	Regional ISP
/13	255.248.0.0	0.7.255.255	524,288	524,286	1/2048	Large ISP
/12	255.240.0.0	0.15.255.255	1,048,576	1,048,574	1/4096	Very large ISP
/11	255.224.0.0	0.31.255.255	2,097,152	2,097,150	1/8192	National ISP
/10	255.192.0.0	0.63.255.255	4,194,304	4,194,302	1/16384	Tier 1 ISP
/9	255.128.0.0	0.127.255.255	8,388,608	8,388,606	1/32768	Continental ISP
/8	255.0.0.0	0.255.255.255	16,777,216	16,777,214	1/65536	Class A network

Note: /31 subnets (RFC 3021) do not reserve network and broadcast addresses, allowing 2 usable hosts on point-to-point links.

IPv6 Prefix Length Reference

Prefix	Addresses	Typical Assignment	Description
/128	1	Host address	Single IPv6 address
/127	2	Point-to-point link	Router interconnect
/64	18.4 quintillion	LAN segment	Standard subnet size
/56	4.7 sextillion	Home network	Residential allocation
/48	1.2 nonillion	Organization	Enterprise allocation
/32	7.9 undecillion	ISP allocation	Regional registry

Private IP Address Ranges (RFC 1918)

Class A Private

10.0.0.0/8

Range: 10.0.0.0 - 10.255.255.255

Hosts: 16,777,214

Use: Large enterprises, data centers

Class B Private

172.16.0.0/12

Range: 172.16.0.0 - 172.31.255.255

Hosts: 1,048,574

Use: Medium enterprises, campus networks

Class C Private

192.168.0.0/16

Range: 192.168.0.0 - 192.168.255.255

Hosts: 65,534

Use: Home networks, small offices

Special Use Ranges

127.0.0.0/8 - Loopback

169.254.0.0/16 - Link-local

224.0.0.0/4 - Multicast

240.0.0.0/4 - Reserved

Professional IP Subnet Calculator & Network Planning Tool

The IP Subnet Calculator is a comprehensive network engineering tool designed for IT professionals, network architects, and Cisco engineers. This advanced calculator supports both IPv4 and IPv6 protocols, offering enterprise-grade features including VLSM calculations, supernet optimization, subnet overlap detection, and automatic Cisco IOS configuration generation.

Advanced Network Engineering Features

Our calculator delivers professional-grade functionality specifically designed for complex network environments:

Complete Subnet Analysis: Instantly compute network addresses, broadcast addresses, usable host ranges, wildcard masks, and subnet boundaries for IPv4 and IPv6 networks with mathematical precision.
Cisco IOS Integration: Generate production-ready Cisco router and switch configurations including interface assignments, routing table entries, and Access Control Lists compatible with IOS, IOS-XE, and NX-OS platforms.
Variable Length Subnet Masking (VLSM): Optimize IP address allocation with efficient VLSM calculations that minimize address waste and support hierarchical network designs.
Route Summarization & Supernetting: Calculate optimal supernet routes for BGP, OSPF, and EIGRP implementations to reduce routing table size and improve network performance.
Network Validation Tools: Detect subnet overlaps, validate CIDR blocks, and ensure clean network segmentation before implementation.
Visual Network Diagrams: Generate ASCII network topology diagrams for documentation, troubleshooting guides, and network change requests.

Enterprise Network Design Applications

This tool addresses critical network planning challenges in enterprise environments:

Data Center Design: Plan multi-tier architectures with proper subnet allocation for management, storage, compute, and DMZ networks.
Campus Network Segmentation: Design VLAN structures with appropriate subnet sizes for different departments, guest networks, and IoT devices.
WAN Connectivity Planning: Calculate point-to-point link addressing (/30, /31) for MPLS, SD-WAN, and traditional WAN connections.
Cloud Network Integration: Plan hybrid cloud connectivity with proper subnet allocation for AWS VPCs, Azure VNets, and Google Cloud networks.
Security Zone Implementation: Design network segmentation for PCI DSS compliance, zero-trust architectures, and microsegmentation strategies.
IPv6 Migration Planning: Plan dual-stack implementations with proper IPv6 prefix allocation and transition mechanisms.

Cisco Certification & Training Support

Essential tool for Cisco certification preparation and ongoing professional development:

CCNA Preparation: Master subnetting fundamentals, VLSM concepts, and basic routing protocols with interactive examples.
CCNP Enterprise/Security: Advanced routing optimization, complex VLSM scenarios, and enterprise network design principles.
CCIE Lab Preparation: High-speed subnet calculations, complex addressing schemes, and troubleshooting scenarios.
Network Troubleshooting: Quickly identify addressing conflicts, routing issues, and connectivity problems in production environments.

Whether you're designing enterprise networks, preparing for Cisco certifications, or troubleshooting complex addressing issues, this calculator provides the professional-grade tools and accuracy required for mission-critical network infrastructure.