"Cannot create External Network. Existing network backings in use or is an uplink" error when creating an external network in VMware Cloud Director.

Products

• VMware Cloud Director

Issue/Introduction

Symptoms:

• Creating an external network in VMware Cloud Director fails with the error

Cannot create External Network. Existing network backings in use or is an uplink. Possible solution would be to configure overlapping networks (i.e if you wish to use the same VLAN ID)".

Environment

VMware Cloud Director 10.x

Cause

This issue happens when a new external network that run on the same network segment as an existing one is created.

Resolution

To resolve this issue, enable the General setting to allow overlapping networks before creating the external network:

1. On the Provider Portal > Administration tab > Settings > General > in the Networking section, click the Edit button.
2. Enable the Allow Overlapping External Networks toggle and click Save.
3. Overlap External Networks should now be set to Enabled.
4. Create the external network from the VMware Cloud director UI/API.

Additional Information

The details of the General settings are documented in https://docs.vmware.com/en/VMware-Cloud-Director/10.3/VMware-Cloud-Director-Service-Provider-Admin-Portal-Guide/GUID-52098C1B-44F4-4524-91B3-C64B9C06F655.html?hWord=N4IghgNiBcIIIQgewO4AIDyA3ApgJwjAAciBLAOwHM0BRADwBd9zI0A5HBlJPAawGcQAXyA