Cross-vCenter NSX fails with error overlapping segment IDs

Products

• VMware NSX

Issue/Introduction

• NSX for vSphere  6.4.x configured for cross vCenter (multisite)
• Web UI method to evaluate if overlapping segment id pools 
• Validate the issue is present as follows

1. On the Web Client go to Networking and Security -> Installation -> Logical Network Preparation -> Segment ID (tab) -> click the appropriate NSX manager.
2. Click the edit button
3. This problem exists if there us difference between the Segment IDs displayed in the pop up window "Edit Segment IDs and Multicast Address Allocation" compared to the range visible on the segment id page. Overlapping or an incorrect segment id pool has been applied. The segment id pool in the pop up edit window will be the last segment id pool applied via REST API. 
   
   

Environment

VMware NSX for vSphere 6.4.x

Resolution

To resolve the issue, delete the overlapping segment id pool through REST API.

1. DELETE https://NSX_MANAGER/api/2.0/vdn/config/segments/3 (input segment id number, only number, this example used 3)
2. Confirm delete was successful running the same REST API GET command above.
3. GET https://NSX_MANAGER/api/2.0/vdn/config/segments
    

   <?xml version="1.0" encoding="UTF-8"?>
   <segmentRanges><segmentRange>
   <id>1</id>
   <name>5000-5999</name>
   <begin>5000</begin>
   <end>5999</end>
   <isUniversal>false</isUniversal>
   <universalRevision>0</universalRevision><
   /segmentRange>
   </segmentRanges>

   Here,the segment id 3 is no longer available, and has been successfully deleted.

4. Confirm the segment id was deleted by using the web UI. Go to Networking and Security -> Installation -> Logical Network Preparation -> Segment ID (tab) -> click the appropriate NSX manager. Click the edit button, the segment id's in the pop up window "Edit Segment IDs and Multicast Address Allocation" should match the range inputted on the segment id page.