Duplicate IP address or APIPA IP address are assigned to Virtual Machines when we move a Segment with Gateway DHCP Server to a Different Gateway

Products

• VMware NSX

Issue/Introduction

• NSX segments are configured to use Gateway DHCP server to get IP address for Virtual Machines.
• Issue is observed when we change the gateway of the segment from one Tier-0/Tier-1 to another Tier-0/Tier-1.
• VM might end up getting duplicate or APIPA IP.
• Below warning message would also be shown in the NSX UI when we change the Gateway connected to the Segment with Gateway DHCP configured.
  
  

Environment

VMware NSX

Cause

• This issue occurs because the DHCP leases is not synchronized between Old Tier-0/Tier-1 and new Tier-0/Tier-1 after the gateways are changed for Segment with Gateway DHCP enabled.
• There will DHCP lease issue or IP assignment issues if we change the Gateway (Tier-0/Tier-1) connected to the Segment to another Gateway(Tier-0/Tier-1).
• The Newly attached Tier1/Tier0 to the segment is unaware of the leases issued by its predecessor (previous Tier-0/Tier-1), and the New Tier-0/Tier-1 Gateway may assign an IP address that is currently in use by a another VM (for which the same IP was allocated by the old Tier1/Tier0).

Resolution

• This is expected behavior when you change the Tier-0/Tier-1 of a Segment when Gateway DHCP is being used.
  
  https://techdocs.broadcom.com/us/en/vmware-cis/nsx/vmware-nsx/4-2/administration-guide/nsx-dhcp-policy-ui/scenarios-impact-of-changing-segment-connectivity-on-nsx-dhcp.html (Scenario 1: Move a Routed Segment with Gateway DHCP Server to a Different Gateway)

Additional Information

Similar issue is also see when the Edge Cluster or HA mode is changed for the Tier-0/Tier-1 connected to Segment with Gateway DHCP enabled. https://knowledge.broadcom.com/external/article?articleNumber=414800