Range Overlap Checker
Detect intersecting address ranges.
Range Overlap Checker: inputs and results
Enter an IP address, CIDR prefix, or range. Then check its first and last address below.
Calculated Boundaries & ParametersReady
Key Capabilities
- •100% Client-Side: Zero telemetry or server latency.
- •RFC Compliant: Exact 32-bit and 128-bit integer precision.
- •Quick Copy: Instant access to CIDR, mask, and range bounds.
- •Cross-Platform: Works on desktop, tablet, and mobile browsers.
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Subnet Boundary Checker
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IP-in-Range Checker
Test whether an address belongs.
IP-in-Subnet Checker
Test membership within a CIDR block.
How Range Overlap Checker Works?
This tool works by testing whether each range starts before the other range ends. Both conditions true means the ranges share at least 1 address.
Enter range A
Type
10.0.0.100 – 10.0.0.200.Enter range B
Type
10.0.0.150 – 10.0.1.10.Compare endpoints
A starts before B ends, and B starts before A ends.
Report the overlap
The checker returns Overlap, the shared range
10.0.0.150 – 10.0.0.200, and its size, 51 addresses.
Range Overlap Checker Formula
The formula is Overlap = (Start_A ≤ End_B) AND (Start_B ≤ End_A).
Overlap test
S_A ≤ E_B AND S_B ≤ E_ATrue for any shared address.
Overlap size
min(E_A, E_B) − max(S_A, S_B) + 1Valid when the test is true.
Adjacent, no overlap
E_A + 1 = S_BRanges touch without sharing.
Worked example: 10.0.0.100–10.0.0.200 vs 10.0.0.150–10.0.1.10
S_A ≤ E_B → 10.0.0.100 ≤ 10.0.1.10 ✓ S_B ≤ E_A → 10.0.0.150 ≤ 10.0.0.200 ✓ Shared = 10.0.0.150 – 10.0.0.200 Size = 51 addresses
Range Overlap Checker Conversion Table
The table tests 8 pairs of IPv4 ranges and shows the overlap size of each pair.
| Range A | Range B | Overlap | Shared Addresses |
|---|---|---|---|
| 10.0.0.100 – 10.0.0.200 | 10.0.0.150 – 10.0.1.10 | Yes | 51 |
| 10.0.0.0 – 10.0.0.127 | 10.0.0.128 – 10.0.0.255 | No | 0 |
| 10.0.0.0 – 10.0.0.255 | 10.0.0.64 – 10.0.0.95 | Yes | 32 |
| 192.168.1.1 – 192.168.1.50 | 192.168.1.50 – 192.168.1.99 | Yes | 1 |
| 172.16.0.0 – 172.16.3.255 | 172.16.2.0 – 172.16.5.255 | Yes | 512 |
| 10.1.0.0 – 10.1.0.10 | 10.2.0.0 – 10.2.0.10 | No | 0 |
| 203.0.113.0 – 203.0.113.255 | 203.0.113.0 – 203.0.113.255 | Yes | 256 |
| 198.51.100.200 – 198.51.101.20 | 198.51.100.0 – 198.51.100.199 | No | 0 |
What is Range Overlap Checker?
The Range Overlap Checker is a tool that detects whether 2 IPv4 address ranges share any addresses, and how many.
Overlapping ranges cause duplicate DHCP leases, conflicting static assignments, and ambiguous firewall rules. The checker uses 2 comparisons that work for every range shape, aligned or not.
Ranges that touch but do not share an address, such as .0 – .127 and .128 – .255, are reported as no overlap. The Adjacent Range Checker covers that case.
What are the uses of Range Overlap Checker?
There are 4 main uses of the Range Overlap Checker, including DHCP pool checks, static plan reviews, and partner ranges.
Checking DHCP pools
Two DHCP servers with overlapping pools hand out the same address twice.
Reviewing static assignments
Static blocks that overlap a DHCP pool lead to conflicts.
Comparing partner ranges
Partner networks with overlapping ranges need NAT before connecting.
Validating range imports
Imported range lists are checked for internal overlaps.