Free Online IP Subnet Calculator
Use our free IP Subnet Calculator to calculate IPv4/IPv6 subnets, CIDR notation, VLSM, supernetting, and network analysis. Perfect for network engineers, IT professionals, and students. Fast, accurate, and easy to use online.
How to Use Our IP Subnet Calculator
Enter IP Address
Input your IPv4 or IPv6 address in the calculator
Set Subnet Mask or CIDR
Enter subnet mask or CIDR prefix length
Calculate Results
Click calculate to get comprehensive network analysis
Analyze Network
Review network address, broadcast, host range, and more
Supported Network Types & Features
IPv4 Subnet Calculator
Calculate IPv4 subnets with CIDR notation
192.168.1.0/24
IPv6 Subnet Calculator
Calculate IPv6 subnets and prefixes
2001:db8::/64
CIDR Calculator
Classless Inter-Domain Routing notation
/24, /16, /8
VLSM Calculator
Variable Length Subnet Masking
Different masks per subnet
Supernet Calculator
Combine multiple networks
Route aggregation
Network Analysis
Comprehensive network analysis
Host count, ranges
Binary Calculator
Binary representation of IPs
11000000.10101000
Hex Calculator
Hexadecimal IP conversion
C0A80100
Security Analysis
Network security assessment
Private vs public IPs
IPv4 Network Classes & Private Ranges
Class A Networks
Class B Networks
Class C Networks
Class D (Multicast)
Class E (Reserved)
Loopback
Advanced Network Calculation Features
Network Address Calculation
Calculate network address using IP and subnet mask
Broadcast Address
Determine broadcast address for the subnet
Host Range Analysis
Calculate usable host addresses and ranges
Binary & Hex Conversion
Convert between decimal, binary, and hexadecimal
Frequently Asked Questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation is a method for specifying IP addresses and their routing prefix. It uses a slash followed by a number (e.g., /24) to indicate the number of network bits.
What is the difference between IPv4 and IPv6?
IPv4 uses 32-bit addresses (4.3 billion addresses) while IPv6 uses 128-bit addresses (340 undecillion addresses). IPv6 provides better security, auto-configuration, and eliminates the need for NAT.
What is VLSM?
VLSM (Variable Length Subnet Masking) allows you to use different subnet masks for different subnets within the same network, enabling more efficient use of IP addresses.
How do I calculate usable hosts?
Usable hosts = 2^(host bits) - 2. The minus 2 accounts for the network address and broadcast address which cannot be assigned to hosts.
What is supernetting?
Supernetting is the process of combining multiple smaller networks into a larger network by reducing the subnet mask length, allowing for more efficient routing and address allocation.
What are private IP addresses?
Private IP addresses are reserved ranges that cannot be routed on the internet: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. They are used for internal networks and require NAT for internet access.
How do I calculate subnet mask from CIDR?
For a /24 CIDR, the subnet mask is 255.255.255.0. The number after the slash indicates how many bits are used for the network portion, with the remaining bits for hosts.
What is the difference between network and broadcast addresses?
The network address is the first address in a subnet (all host bits are 0), while the broadcast address is the last address (all host bits are 1). Neither can be assigned to hosts.
How do I calculate wildcard mask?
Wildcard mask is the inverse of subnet mask. For subnet mask 255.255.255.0, the wildcard mask is 0.0.0.255. It's used in routing protocols and access lists.
What is the purpose of subnetting?
Subnetting divides a large network into smaller, manageable subnets. It improves security, reduces broadcast traffic, optimizes routing, and allows for better network organization and management.
How do I determine the number of subnets?
Number of subnets = 2^(subnet bits). The subnet bits are the additional bits borrowed from the host portion to create subnets within the original network.
What is the difference between classful and classless addressing?
Classful addressing uses fixed network classes (A, B, C), while classless addressing (CIDR) allows variable-length subnet masks, providing more flexibility and efficient address allocation.
How do I calculate network address?
Network address = IP address AND subnet mask. This operation results in the network portion of the address with all host bits set to zero.
What is the maximum number of hosts in a subnet?
Maximum hosts = 2^(host bits) - 2. The minus 2 accounts for the network and broadcast addresses. For example, a /24 subnet has 2^8 - 2 = 254 usable hosts.
How do I convert between decimal and binary IP addresses?
Each octet (8 bits) is converted separately. For example, 192 = 11000000 in binary. Our calculator automatically shows both decimal and binary representations for easy conversion.
What are the benefits of IP subnetting?
IP subnetting provides efficient IP usage by optimizing address allocation, enhanced security through network segmentation and access controls, and improved performance by reducing broadcast domains and improving routing efficiency.
How do I manually calculate subnets step by step?
Step 1: Convert IP address to binary. Step 2: Apply subnet mask. Step 3: Calculate network address using AND operation. Step 4: Calculate broadcast address by setting all host bits to 1. Step 5: Calculate usable host range excluding network and broadcast addresses.
What is the CIDR conversion table for common subnet masks?
/30 = 255.255.255.252 (2 hosts), /28 = 255.255.255.240 (14 hosts), /24 = 255.255.255.0 (254 hosts), /20 = 255.255.240.0 (4,094 hosts), /16 = 255.255.0.0 (65,534 hosts).
How does VLSM improve IP address efficiency?
VLSM allows different subnet masks for different subnets within the same network, enabling more efficient IP address allocation. For example, a sales department can use /26 (62 hosts) while IT uses /28 (14 hosts) from the same /24 network.
What is the difference between IPv4 and IPv6 subnetting?
IPv4 uses 32-bit addresses with subnet masks, while IPv6 uses 128-bit addresses with prefix lengths. IPv6 provides much larger address space (340 undecillion vs 4.3 billion), better security features, and eliminates the need for NAT.
How do I design a network with proper subnetting?
Consider user requirements (current and future host count), security zones (DMZ, internal, management, guest networks), and performance needs (broadcast domain size, routing efficiency). Plan for 20-30% growth and use consistent subnet sizes where possible.
What are the security benefits of subnetting?
Subnetting enhances security through network segmentation (isolate critical systems), access control (implement VLANs and ACLs), threat containment (limit blast radius of attacks), and compliance (meet regulatory requirements and maintain audit trails).
What are the best practices for subnet design?
Planning: Document requirements, plan for growth, use consistent sizes, reserve IP ranges. Implementation: Start with largest subnets, use VLSM, implement gradually, test thoroughly. Management: Maintain documentation, use IPAM tools, monitor utilization, conduct regular audits.
How do I troubleshoot common subnetting problems?
For hosts that can't communicate: Check if hosts are in same subnet, verify subnet mask configuration, ensure default gateway is correct, check for IP conflicts. For routing issues: Verify route table entries, check for overlapping subnets, ensure proper supernetting, validate next-hop addresses.
What diagnostic commands help with subnet troubleshooting?
Windows: ipconfig /all, ping [destination], tracert [destination], route print. Linux: ip addr show, ping [destination], traceroute [destination], ip route show. These commands help verify IP configuration, test connectivity, trace routing paths, and display routing tables.
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