ESXi host networking fails after bios update on Dell PowerEdge server connected to Juniper network switch

Products

• VMware vSphere ESXi

Issue/Introduction

After performing a BIOS update and subsequent reboot of a Dell PowerEdge server running VMware ESXi 8.x, the host loses all network connectivity. Symptoms include:

• The ESXi host disconnects from vCenter Server.
• Management network tests from the Direct Console User Interface (DCUI) fail.
• Pings from the ESXi shell to the gateway or other network devices fail.
• Dell iDRAC shows physical NIC status as **Connected** with an active link.
• The issue persists even after rolling back the BIOS update or performing a clean reinstallation of ESXi.
• Installing a different operating system (e.g., CentOS) on the same hardware results in the same lack of connectivity.

Environment

• ESXi 8.x
• ESX 9.x

Cause

This issue is typically caused by a known bug in the **Junos** operating system on upstream **Juniper** network switches. 

When the ESXi host reboots (triggered by the BIOS update process), the physical port on the Juniper switch may enter a hung state. While the physical layer (Layer 1) may report a link, the switch port stops forwarding traffic. This state is maintained by the switch and is independent of the host's operating system or BIOS version.

Resolution

Consult Juniper support to identify if a Junos update is available to resolve this specific SFP port hang bug.