Identifying Overlapping Subnets

tmotofga

Greetings,

Just putting it out here. Has anyone found a way to identify overlapping subnets in SolarWinds Observability ver 2026.x?

I fund this in ChatGPT, but it does not work in 2026.x

Creating a Report of Overlapping DHCP Scopes in SolarWinds IPAM

Objective

This report identifies overlapping DHCP scopes discovered in SolarWinds IP Address Manager (IPAM). Overlapping scopes can cause duplicate IP assignments, DHCP conflicts, and client connectivity issues.

Method 1 – Using the Built-In SolarWinds IPAM Interface

Step 1 – Open IPAM

1. Log in to the SolarWinds Orion Web Console.
2. Navigate to:
   • My Dashboards → IP Addresses → Manage Subnets & IP Addresses

Step 2 – Review Existing Scopes

1. Expand the subnet tree.
2. Identify DHCP-managed subnets.
3. Look for:
   • Duplicate subnet ranges
   • Nested subnets
   • Identical superscopes
   • Overlapping CIDR blocks

Example:

Scope A	Scope B	Issue
192.168.1.0/24	192.168.1.128/25	Overlap
10.1.1.0/24	10.1.1.0/25	Overlap

Method 2 – Create a Custom SQL Report in SolarWinds

Create the Report

1. Navigate to:
   • Reports → All Reports → Create New Report
2. Select:
   • Custom Table
3. Choose:
   • Advanced Database Query (SQL/SWQL)

Recommended SWQL Query

SELECT    s1.SubnetAddress AS Scope1,    s1.CIDR AS Scope1CIDR,    s2.SubnetAddress AS Scope2,    s2.CIDR AS Scope2CIDR,    s1.DisplayName AS Scope1Name,    s2.DisplayName AS Scope2NameFROM IPAM.Subnets s1JOIN IPAM.Subnets s2ON s1.SubnetId <> s2.SubnetIdWHERE(    IPAddressToInteger(s1.SubnetAddress) <= IPAddressToInteger(s2.BroadcastAddress)    AND    IPAddressToInteger(s1.BroadcastAddress) >= IPAddressToInteger(s2.SubnetAddress))ORDER BY s1.SubnetAddress

What This Query Does

The query:

• Compares every subnet against every other subnet
• Detects overlapping IP ranges
• Excludes self-comparisons
• Displays both subnet names and CIDR values

Optional Enhancements

Add DHCP Server Information

SELECT    s.DisplayName,    s.SubnetAddress,    s.CIDR,    d.ServerNameFROM IPAM.Subnets sLEFT JOIN IPAM.DHCPScopes dON s.SubnetId = d.SubnetId

Filter Only Active DHCP Scopes

Add:

AND d.Enabled = 'True'

Recommended Report Layout

Scope Name	Network	CIDR	DHCP Server	Overlap With
Atlanta-Users	10.10.1.0	/24	DHCP01	10.10.1.128/25

Best Practices

• Avoid overlapping scopes across failover pairs.
• Verify superscopes carefully.
• Audit VPN and guest VLAN DHCP ranges.
• Export the report weekly.
• Schedule alerts for newly discovered overlaps.

Scheduling the Report

1. Go to:
   • Reports → Manage Reports
2. Select the report.
3. Click:
   • Schedule Report
4. Configure:
   • PDF or HTML output
   • Email recipients
   • Daily or weekly execution

Alternative PowerShell Validation

If you want to validate overlaps directly against Microsoft DHCP servers:

Get-DhcpServerv4Scope -ComputerName DHCP01 |Select ScopeId, StartRange, EndRange

You can export the results and compare ranges against SolarWinds IPAM data.

Troubleshooting

Query Returns No Results

• Verify IPAM polling is current.
• Confirm DHCP scopes are imported.
• Ensure SWQL Studio access is working.

Duplicate Results

Because subnet comparisons are bidirectional, you may see duplicate overlap entries.

To suppress duplicates, add:

AND s1.SubnetId < s2.SubnetId

Recommended Final Query

SELECT    s1.DisplayName AS Scope1Name,    s1.SubnetAddress AS Scope1,    s1.CIDR AS Scope1CIDR,    s2.DisplayName AS Scope2Name,    s2.SubnetAddress AS Scope2,    s2.CIDR AS Scope2CIDRFROM IPAM.Subnets s1JOIN IPAM.Subnets s2ON s1.SubnetId < s2.SubnetIdWHERE(    IPAddressToInteger(s1.SubnetAddress) <= IPAddressToInteger(s2.BroadcastAddress)    AND    IPAddressToInteger(s1.BroadcastAddress) >= IPAddressToInteger(s2.SubnetAddress))ORDER BY s1.SubnetAddress

Outcome

This report provides:

• Identification of overlapping DHCP scopes
• Visibility into conflicting subnet assignments
• Better DHCP hygiene and IPAM accuracy
• Easier troubleshooting of duplicate IP conflicts

Thanks,