ESXi host disconnects during cross vCenter migration due to Port 902 network mismatch
Article ID: 449222
Updated On:
Products
Issue/Introduction
When migrating ESXi hosts from an old vCenter to a new vCenter instance, the hosts may intermittently disconnect or fail to stay connected. This typically occurs when the networking environment changes (e.g., from Layer 2 to Layer 3 connectivity) between the host and the new vCenter Server. The following behaviors may be seen:
- ESXi hosts show as "Not Responding" or "Disconnected" shortly after being added to the new vCenter.
- Cross vCenter vMotion tasks fail or time out.
- Connectivity tests to the host on port 902 fail.
Environment
- VMware vCenter Server 7.x / 8.x
- VMware vSphere ESXi 7.x / 8.x
- Cross vCenter Server Migration
Cause
The issue is caused by network configuration mismatches between the source and destination environments. Specifically, if the host was previously on a Layer 2 segment with the old vCenter but is now communicating across a Layer 3 boundary with the new vCenter, firewall rules or routing may block essential traffic on TCP/UDP Port 902 (NFC/Heartbeats).
Resolution
To resolve the intermittent disconnection, verify and open the required network ports between the ESXi host and the new vCenter Server.
- Log in to the ESXi host shell via SSH.
- Test connectivity from the host to the new vCenter Server on port 902 using the following command:
nc -zv <vCenter_IP_Address> 902 - If the connection fails or times out, engage your network administration team to ensure Port 902 is open bidirectionally between the host management network and the vCenter Server network.
- Ensure that any Layer 3 routing devices or firewalls between the segments are configured to allow Heartbeat and NFC traffic.
- Verify that the MTU settings are consistent across the physical and virtual switches in the new network path.
For more information on migration requirements, see Cross vCenter Migration and Clone requirements in VMware vSphere 6.x and later
Additional Information
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