X scopes has not been added because it is overlapping with existing subnet

This article shows how to resolve the following error when adding discovered scopes overlapping with existing subnets: 

X scopes has not been added because it is overlapping with existing subnet.

On some cases, some scopes could not be added because they do not fit cleanly into the available subnet space.

Symptoms:

• Some DHCP scopes fail to be added because their IP ranges overlap with existing subnets.
• IPAM does not update or add the overlapping scopes, leading to incomplete subnet information.
• Potential IP address conflicts or routing issues may arise due to overlapping subnet ranges.
• DHCP scans may show mismatched or duplicated scopes if replicating DHCP servers are involved.

This issue occurs because IPAM prevents adding scopes that overlap with existing subnets to avoid IP address conflicts and routing issues. Overlapping scopes can cause inaccurate IP address tracking and potential network conflicts.

1. Ensure that the scope is expanded or contracted both ways or in one direction.
2. Modify either the start or the end IP address one at a time and immediately apply the changes after each and every change to the start or end IP address of the scope.
3. If two stand-alone DHCP servers are servicing the same subnet, ensure that you are not overlapping the available pool on each DHCP server as they do NOT share the DHCP database and are not aware of the leases that are assigned. By excluding addresses, you ensure that IPs will not be offered that may otherwise be in use.  
4. Drop the subnet from IPAM. Then rescan the DHCP server and have the scope pulled into IPAM where it will create a new subnet in which to fit itself.
5. Enable duplicate subnets by clicking Settings > All Settings > IPAM Settings >  System Settings. Check the box for Enable Duplicate Subnets and save, then have the new scope exist in its own subnet.