ESXi Hosts intermittently disconnecting from vCenter when using iSCSI port binding

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

• Within the vCenter GUI, you observe ESXi hosts that intermittently switch between showing as disconnected and showing as connected. 
• You have multiple kernel ports in the same IP subnet, using the same TCP/IP stack, and are configured together for iSCSI port binding.  This is a perfectly acceptable exception to the rule that states: "Configurations with more than one vmknic in the same IP subnet and TCP/IP stack are not supported."  See Multihoming on ESXi.  

  

Environment

VMware vSphere ESXi 
VMware vCenter Server

Cause

• Despite the fact that having multiple kernel ports configured for iSCSI port binding in the same IP subnet and TCP/IP stack IS supported, this is no longer that case when the vmkernel ports are assigned with the Management service.  See the screenshot within the Issue/Introduction section for an example of this non-supported configuration. 

Resolution

• It is not possible to remove the Management service from a vmkernel used for iSCSI networking unless the port binding for the vmkernel port is removed first.  See below for the steps to remove the port binding from the desired vmkernel port:
  1. Click Storage in the VMware Host Client inventory, click Adapters, and then click Configure iSCSI.
  2. In the Network port bindings section, select a VMkernel NIC from the list.
  3. Click Remove port binding. 
  4. Click Save configuration.

Additional Information

See "Configuring Software iSCSI Adapters in the VMware Host Client" for more information about Configuring or removing iSCSI port bindings.