IP Subnet Calculator: Calculate Network Range & CIDR
Calculate IP subnets, ranges, and network information by entering an IP address and subnet mask below.
Understanding IP Addresses and Subnetting
IP addressing and subnetting are fundamental concepts in computer networking that enable devices to communicate effectively across networks. Understanding these concepts is crucial for network administrators, IT professionals, and anyone working with computer networks.
IP Address Basics
| Concept | Description | Example |
|---|---|---|
| IPv4 Format | 32-bit number expressed in four octets | 192.168.1.1 |
| Address Classes | Traditional division of IP ranges | Class A, B, C, D, E |
| Private Ranges | Reserved for internal network use | 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 |
Understanding Subnet Masks
A subnet mask determines which portion of an IP address identifies the network and which portion identifies the host. Common subnet masks and their applications:
| CIDR Notation | Subnet Mask | Available Hosts | Typical Use Case |
|---|---|---|---|
| /24 | 255.255.255.0 | 254 | Small to medium LAN |
| /16 | 255.255.0.0 | 65,534 | Large corporate network |
| /8 | 255.0.0.0 | 16,777,214 | Major network backbone |
| /30 | 255.255.255.252 | 2 | Point-to-point links |
Network Planning Considerations
When planning network subnets, consider these key factors:
| Factor | Consideration | Impact |
|---|---|---|
| Network Size | Current and future host requirements | Determines subnet mask selection |
| Network Growth | Anticipated expansion needs | Affects address space allocation |
| Security | Network segmentation requirements | Influences subnet organization |
Frequently Asked Questions
What is CIDR notation?
CIDR (Classless Inter-Domain Routing) notation is a compact method for specifying IP addresses and their associated routing prefix. It appends a slash followed by the number of leading 1 bits in the routing prefix mask to the address. For example, 192.168.1.0/24 represents the IPv4 address 192.168.1.0 and its associated routing prefix 255.255.255.0.
How do I calculate the number of available hosts?
To calculate the number of available host addresses in a subnet:
- Subtract the CIDR number from 32 (for IPv4)
- Calculate 2 raised to that power
- Subtract 2 (for network and broadcast addresses)
Example: For a /24 network:
32 - 24 = 8
2^8 = 256
256 - 2 = 254 available hosts
What's the difference between public and private IP addresses?
Public IP addresses are globally unique and routable on the internet. Private IP addresses are used within local networks and cannot be routed directly on the internet. Private IP ranges are:
- 10.0.0.0 to 10.255.255.255 (10.0.0.0/8)
- 172.16.0.0 to 172.31.255.255 (172.16.0.0/12)
- 192.168.0.0 to 192.168.255.255 (192.168.0.0/16)
What is a network address?
A network address is the first address in a subnet and identifies the network itself. It's calculated by performing a bitwise AND operation between an IP address and its subnet mask. Network addresses cannot be assigned to devices.
What is a broadcast address?
The broadcast address is the last address in a subnet, used to send packets to all hosts in the subnet. It's calculated by setting all host bits to 1 in the network address. Like network addresses, broadcast addresses cannot be assigned to devices.
Best Practices for Subnetting
Plan for Growth: Always allocate more IP addresses than currently needed to accommodate future growth.
Document Everything: Maintain detailed documentation of your IP address allocation and subnet assignments.
Use VLSM: Variable Length Subnet Masking allows for more efficient use of IP address space by using different subnet masks for different networks.
Consider Security: Use subnetting to create security zones and isolate sensitive networks.
Common Subnetting Problems and Solutions
| Problem | Cause | Solution |
|---|---|---|
| IP Conflicts | Overlapping subnets | Proper subnet planning and documentation |
| Limited Growth | Insufficient address space | Use larger subnet or implement VLSM |
| Poor Performance | Too many hosts in subnet | Break into smaller subnets |