Transport Nodes lost connection to NSX Managers

Products

• VMware NSX

Issue/Introduction

• Below failure message could be seen for the host Transport node

Heartbeating between NSX management node and host <host-UUID> is down

Host configuration: Failed to send the HostConfig message. [TN=TransportNode/<TN-UUID>]. Reason: Failed to send HostConfig RPC to MPA TN:<TN-UUID>.

• Similar log messages under /var/log/syslog.log on NSX Manager 

2025-12-11T11:14:47Z: <TN-UUID> (UNKNOWN): MPA is DOWN = Client has not responded to {2} consecutive heartbeats. Port {1234} between Host to NSX Manager must be open, Please check underlay physical firewalls and host hypervisor firewalls for troubleshooting.

• There are Expired TN certificate and have not been replaced yet 

 

Environment

VMware NSX 4.x

Cause

Expired APH-TN certificate preventing Host Transport nodes from re-connecting to the NSX Managers on port 1234 and 1235

Resolution

• Replace the expired certificates with a new one and Resolve the alarm under (System --> Fabric --> Hosts) to re-establish connection.
• Make sure to check alarms for any certificate approaching expiry date and Refer: Using Certificate Analyzer, Results and Recovery (CARR) Script to fix certificate related issues in NSX
   

Additional Information

Alarm For Transport Node Certificate Has Expired.

Connection between host and NSX Controller is UNKNOWN due to connection between host and NSX Manager is DOWN

Heartbeating between NSX management node and host &lt;host-UUID&gt; is down.