Unable to connect with logical switch "uuid" already connected to logical router port error when creating a new external interface on T0-VRF instance

Products

• VMware NSX

Issue/Introduction

• You have created a Tier-0 gateway of type VRF.
• You are adding interface to the VRF instance. 
• The interface is connected to a non-trunk VLAN segment. 
• New interface is in a Failed state with the following error:
  Jun 2, 2025, 9:45:00 AM : [error_code=10010, module_name=ROUTING, error_message='[Routing] Unable to connect with logical Switch "<UUID_of_the_uplink_segment_used_by_this interface>" already connected to logical router port <existing_tier-0_uplink_interface_UUID>.']
[Routing] Unable to connect with logical Switch "<UUID_of_the_uplink_segment_used_by_this interface>" already connected to logical router port <existing_tier-0_uplink_interface_UUID>.
  
  
  

Environment

VMware NSX

Resolution

Use a dedicated segment in trunk mode. 

Additional Information

Deploy an NSX VRF-Lite with BGP:

• VLAN tagging (802.1q) is used to differentiate traffic among VRFs. The external interface on tier-0 VRF gateway needs to be connected to a trunk segment with the corresponding access VLAN ID defined in the segment VLAN range.

and

• Configure the VLAN trunk segment.
  • In VLAN, enter a list or range of VLAN IDs allowed in the trunk segment.

and

• Configure the external interfaces on the VRF gateway.
  • In Connected To(Segment), select the trunk segment created from Step 2.