NSX overlay tunnels show down between NSX Edges and ESXi transport nodes

Products

• VMware NSX

Issue/Introduction

• Tunnel between the Edge and Transport Nodes is in a down state..
• TEP-to-TEP connectivity  remains functional.
• Alarms indicate heartbeat communication failure between the NSX Edge and the affected ESXi hosts.

Environment

VMware NSX

Cause

The issue is caused by a failure in connection between the Edge node  and the ESXi transport nodes as the nodes where showing as disconnected from NSX manager UI. Even if the data plane (TEP) is healthy, the loss of these heartbeats prevents  from maintaining a synchronized state, leading it to mark the tunnels as down.

Resolution

• Log in to the NSX Manager UI and identify which specific hosts are reporting heartbeat failures.
• Verify the TEP network connectivity between the NSX Manager and the affected ESXi hosts.
• On the affected ESXi hosts, restart  the NSX services(nsx-proxy) if necessary.
• Once communication is restored, the NSX Manager will automatically resynchronize its state and the tunnel status should return to Up. If it does not, navigate to the alarm and manually click Resolve. 

Additional Information

If the tunnels remain down , continue troubleshooting the TEP connectivity to ensure there are no MTU or physical network path issues.

For more information on troubleshooting BFD flaps, Refer: Troubleshooting NSX TEP/BFD Tunnels between ESXi hosts and Edges