NSX Host Node Tunnel Status Degraded Due to Physical NIC Receive CRC Errors.

Products

• VMware NSX

Issue/Introduction

One or more transport nodes appear in a Degraded state when viewed in the NSX UI under Fabric > Hosts. BFD Tunnel status flaps intermittently across multiple ESXi hosts in the cluster.

System logs (vmkernel.log) show events indicating BFD sessions flapping beyond threshold limits and dropping:

2025-10-23T00:36:18.766Z In(182) vmkernel: cpu53:2098407)BFD_HandleStatusChange:873:[nsx@6876 comp="nsx-esx" subcomp="bfd"]local: 10.##.##.67, remote: 10.##.##.38 is flapping beyond 10 times in 5 minutes
2025-10-23T00:36:18.808Z In(182) vmkernel: cpu48:2098407)BFD_HandleStatusChange:873:[nsx@6876 comp="nsx-esx" subcomp="bfd"]local: 10.##.##.67, remote: 10.##.##.166 is flapping beyond 10 times in 5 minutes
2025-10-23T16:49:01.736Z In(182) vmkernel: cpu48:2098407)BFD_HandleStatusChange:851:[nsx@6876 comp="nsx-esx" subcomp="bfd"]local: 10.##.##.67, remote: 10.##.##.38, oldState: up, newState: down, diag: Neighbor Signaled Session Down, type: overlay
2025-10-23T16:49:27.437Z In(182) vmkernel: cpu62:2098407)BFD_HandleStatusChange:851:[nsx@6876 comp="nsx-esx" subcomp="bfd"]local: 10.##.##.67, remote: 10.##.##.166, oldState: up, newState: down, diag: Neighbor Signaled Session Down, type: overlay

Note: The preceding log excerpts are only examples. Date, time, and environmental variables may vary depending on your environment.

Environment

VMware NSX

Cause

The issue is caused by a Layer-1 physical network fault resulting in significant 'Receive CRC errors' on the ESXi host uplink (e.g., vmnic0). The Cyclic Redundancy Check (CRC) mismatch indicates packet corruption at the physical layer, prompting the destination host to discard the packets. This packet loss causes the BFD probes to drop, forcing the peer node to bring the tunnel session down.

Resolution

To resolve this issue, please follow the steps below:

• Identify the impacted uplink by reviewing the ESXi host network statistics. Execute the following command to check for CRC errors: esxcli network nic stats get -n vmnic0
• Monitor the counters to determine if the numbers are actively increasing by executing: watch esxcli network nic stats get -n vmnic0
• If 'Receive CRC errors' are incrementing, inspect the physical cabling, SFP transceivers, and switch ports associated with the impacted vmnic.
• Consult with the hardware vendor to troubleshoot and replace the faulty physical components. These errors are external to the ESXi kernel and are solely reported by the hardware NIC driver. Under normal operating conditions, 'Receive CRC errors' must remain at zero.

 

Additional Information

For more information, please refer to the Knowledge Base (KB) article linked below.

Troubleshooting NIC errors and other network traffic faults in ESXi

NSX Host Node Tunnel Status is 'Degraded'