Error: Card Detected! Cannot allocate WRBs in Emulex elxnet causing host isolation in VMware ESXi 8.x

Products

• VMware vSphere ESXi

Issue/Introduction

VMs on an ESXi 8.x host lose network connectivity (ping loss) and appear disconnected in vCenter Server. The ESXi host may show as "Not Responding" in vCenter, but remains accessible via the Direct Console User Interface (DCUI). In the DCUI, all physical NICs associated with the Emulex adapter may appear in a disconnected state.

Review of vmkernel.log reveals the following signatures:

WARNING: Uplink: #####: Queue 0 of device vmnic0 stuck, resetting the device
WARNING: elxnet: elxnet_txComplClean:####: [vmnic0] #### pending tx-completions on txo[0]
WARNING: elxnet: elxnet_mccWaitCompl:####: [vmnic0] MCC poll timed out!
WARNING: elxnet: elxnet_detectDumpUe:###: [vmnic3] UE Detected!!
WARNING: elxnet: elxnet_detectDumpUe:###: [vmnic3] UE hi: LPCMEMHOST bit set
Error in Card Detected! Cannot allocate WRBs hw_error:0|fw_timeout:1

Environment

ESXi 8.0 Update 3

Cause

The Emulex network adapter enters an Unrecoverable Error (UE) state due to a firmware or hardware lockup. This prevents the elxnet driver from allocating Work Queue Request Blocks (WRBs) through the mailbox interface, resulting in a transmit (TX) hang.

Resolution

To recover a host currently in this state:

1. Perform a Cold Reboot: Power down the ESXi host and physically remove all power cables for at least 30 seconds. A software-initiated warm reboot often fails to clear the hardware registers in a UE state.
2. Align Firmware and Drivers: Ensure the network adapter firmware is at the latest version recommended by the OEM for the installed elxnet driver version.
3. Hardware Diagnostics: If the issue recurs after a cold reboot and update, engage the hardware vendor to inspect or replace the physical NIC.

Additional Information

How to download and install async drivers in VMware ESXi
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