IP Subnet Calculator
Calculate network addresses, host ranges, broadcast addresses, and more from CIDR notation.
CIDR Quick Reference
| CIDR | Subnet Mask | Usable Hosts | Use Case |
|---|---|---|---|
| /32 | 255.255.255.255 | 1 | Single host |
| /31 | 255.255.255.254 | 2 | Point-to-point links |
| /30 | 255.255.255.252 | 2 | Small WAN links |
| /29 | 255.255.255.248 | 6 | Small office |
| /28 | 255.255.255.240 | 14 | Small department |
| /27 | 255.255.255.224 | 30 | Department |
| /26 | 255.255.255.192 | 62 | Workgroup |
| /25 | 255.255.255.128 | 126 | Small building |
| /24 | 255.255.255.0 | 254 | Standard LAN |
| /16 | 255.255.0.0 | 65,534 | Large network |
| /8 | 255.0.0.0 | 16,777,214 | Class A network |
IP Address Classes Explained
Understanding IP address classes helps you design efficient networks and choose the right subnetting strategy for your organization.
| Class | IP Range | Default Mask | Purpose |
|---|---|---|---|
| Class A | 1.0.0.0 – 126.255.255.255 | /8 | Large networks (16M+ hosts) |
| Class B | 128.0.0.0 – 191.255.255.255 | /16 | Medium networks (65K+ hosts) |
| Class C | 192.0.0.0 – 223.255.255.255 | /24 | Small networks (254 hosts) |
| Class D | 224.0.0.0 – 239.255.255.255 | N/A | Multicast |
| Class E | 240.0.0.0 – 255.255.255.255 | N/A | Experimental / Reserved |
Private IP Address Ranges (RFC 1918)
Note: Private IP ranges are reserved for internal networks and are not routable on the public internet. NAT (Network Address Translation) is used to map private addresses to public IPs for internet access.
Best Network Monitoring & Management Tools (2026)
Monitor your subnets, track IP usage, and get alerts for network issues.
| Tool | Type | Price | Key Features | Link |
|---|---|---|---|---|
Datadog Recommended | Network Monitoring | From $15/host/mo | NPM, flow analysis, DNS monitoring, cloud integrations | Visit |
PRTG Network Monitor Paessler AG | All-in-One | Free (100 sensors) / $1,799 | Auto-discovery, bandwidth monitoring, alerting, maps | Visit |
Zabbix Community Edition | Open Source | Free | Template-based monitoring, auto-discovery, distributed monitoring | Visit |
SolarWinds IPAM IP Address Manager | IP Management | Custom pricing | IP address tracking, DHCP/DNS management, subnet scanning | Visit |
ManageEngine OpManager Zoho Corporation | Network Monitoring | From $245 | Network mapping, WAN monitoring, NCM, firewall management | Visit |
Tip: For small to mid-sized networks, PRTG or Zabbix offer excellent free tiers. For enterprise environments with cloud workloads, Datadog provides the most comprehensive network performance monitoring with real-time flow analysis and anomaly detection.
How Subnetting Works: A Quick Guide
What is Subnetting?
Subnetting is the process of dividing a larger IP network into smaller, more manageable sub-networks (subnets). By borrowing bits from the host portion of an IP address and allocating them to the network portion, you create multiple logical networks within a single address space. This is fundamental to efficient network design and IP address management.
Why Subnet?
- ✓Security isolation – Separate sensitive systems (e.g., finance, HR) into dedicated subnets with firewall rules between them.
- ✓Broadcast domain reduction – Smaller subnets mean less broadcast traffic, improving overall network performance.
- ✓Efficient IP allocation – Allocate only the addresses each department or VLAN actually needs, reducing waste.
VLSM (Variable Length Subnet Masking)
VLSM allows you to use different subnet mask lengths within the same network, so each subnet can be sized to fit its actual number of hosts. For example, a point-to-point WAN link only needs a /30 (2 hosts), while an office floor might need a /24 (254 hosts). VLSM prevents wasting addresses by avoiding a one-size-fits-all mask.
Supernetting / CIDR Aggregation
Supernetting (also called route aggregation) is the reverse of subnetting – it combines multiple smaller contiguous networks into a single larger one. For example, four /24 networks (192.168.0.0 through 192.168.3.0) can be summarized as one /22 route. This reduces routing table size and simplifies network management for ISPs and large enterprises.