Understanding IP Address Ranges
In networking, you often need to work with ranges of IP addresses — whether defining firewall rules, configuring subnets, allocating DHCP pools, or specifying access control lists. IP ranges can be expressed in multiple formats, each suited for different purposes.
IP Range Notation Formats
CIDR Notation
Classless Inter-Domain Routing (CIDR) is the standard format for modern networks. The number after the slash indicates how many bits are in the network portion.
Examples: 192.168.1.0/24, 10.0.0.0/8, 172.16.0.0/12
Range Notation
Direct start-to-end specification: 192.168.1.1 - 192.168.1.254
Wildcard Mask
Used in Cisco ACLs (Access Control Lists), a wildcard mask is the bitwise inverse of a subnet mask.
Subnet Mask
Traditional notation still used in many network interfaces and older documentation.
How CIDR Prefix Lengths Work
The prefix length determines how many addresses are in the range:
| CIDR | Addresses | Usable Hosts | Common Use |
|---|---|---|---|
| /8 | 16,777,216 | 16,777,214 | Large enterprise, ISP |
| /16 | 65,536 | 65,534 | Medium organization |
| /24 | 256 | 254 | Small network segment |
| /26 | 64 | 62 | Small VLAN |
| /28 | 16 | 14 | Tiny segment |
| /30 | 4 | 2 | Point-to-point link |
| /32 | 1 | 1 | Host route |
Usable hosts equals total addresses minus 2 (network address and broadcast address).
Converting Between Formats
CIDR to Range
Given 192.168.10.0/25:
- Prefix /25 means 7 host bits
- Total addresses: 128
- Range: 192.168.10.0 to 192.168.10.127
- Usable: 192.168.10.1 to 192.168.10.126
Range to CIDR
Given range 192.168.1.64 to 192.168.1.127:
- Count: 64 addresses
- 64 = 2^6, so 6 host bits
- Prefix: 32 - 6 = /26
- CIDR: 192.168.1.64/26
Private vs. Public IP Ranges
RFC 1918 defines three private IP ranges:
10.0.0.0/8— Large private networks172.16.0.0/12— Medium private networks192.168.0.0/16— Home and small office networks
Additional special ranges include loopback (127.0.0.0/8), link-local (169.254.0.0/16), multicast (224.0.0.0/4), and reserved (240.0.0.0/4).
Practical Use Cases
Firewall Rules
IP range specifications control which networks can access services. Both CIDR notation and explicit ranges are used in firewalls, security groups, and ACLs.
Cloud Security Groups (AWS/GCP/Azure)
Cloud platforms use CIDR notation in security group rules to specify allowed source and destination IP ranges for inbound and outbound traffic.
Web Server IP Restrictions
Nginx and Apache support CIDR-based access control to restrict admin areas or APIs to specific IP ranges.
DHCP Pool Configuration
DHCP servers define address pools using start and end IP addresses, which need to fall within the subnet range but exclude reserved addresses.
Using the IPv4 Range Expander
Our tool helps you:
- Enter a CIDR block and expand it to show all individual IP addresses
- Enter a range (start-end) and convert to CIDR notation
- View network details — network address, broadcast, mask, host count
- Copy expanded list — Export all IPs for use in allow/deny lists
- Check if an IP falls within a given range
The tool handles the binary math automatically, making IP range management accessible even without deep subnetting knowledge. It's ideal for network documentation, firewall rule creation, and subnet planning.