Symptoms:

• When Navigating to Networking and Security > Installation > Host Preparation, you see that a cluster under VXLAN reports Error Unconfigure even when all ESXi hosts are reported as Ready under the installation status.
  
• Clicking the error icon reports the error :
  VTEP has not been created successfully on the Host.
  
• Adding an ESXi host to the cluster reports multiple entries in the task list for task(s) similar to:
  "Add virtual NIC": An error occurred during host configuration.
  
• NSX VIBs are correctly installed on the affected ESXi host that is configured with a VTEP vmkernel interface.
• Rebooting the affected ESXi host does not resolve the issue.
• There are adequate free IP addresses in the IP Pool assigned to the cluster under Networking and Security > Installation > Logical Network Preparation > VXLAN Transport: VMKNic IP Addressing.
  

VMware NSX for vSphere 6.1.x

An ESXi host that had been previously prepared for NSX was removed from the NSX cluster, and then added back to an NSX-prepared cluster (or different cluster) triggering a host preparation activity. When the ESXi host was removed initially, it should have triggered an un-prepare action. However, the un-prepare did not complete successfully, the host was not rebooted to complete the un-preparation, and /or the VXLAN Tunnel End Point (VTEP vmkernel interface removal failed, which causes the host preparation task to fail when trying to re-create the VTEP as it already exist.

To resolve this issue, after removing the ESXi host from an NSX-prepared cluster, ensure that the VTEP vmkernel interface is removed before attempting to add it back into an NSX-prepared cluster.

To manually remove the VTEP vmkernel interface on the ESXi host:

When re-adding a previously prepared ESXi host to an NSX prepared cluster, in addition to the issue described in this article, a situation may occur where the vdl2 module does not load in the correct order. For more information, see Network connectivity issues after upgrading or repreparing ESXi hosts in a VMware NSX/VCNS environment (2107951).

Network connectivity issues after upgrade in NSX/VCNS environment
当将之前置备的 ESXi 主机添加到 VMware NSX for vSphere 6.1.x 的群集中时，VXLAN 的群集状态显示错误：取消配置错误 (Error Unconfigure)
前にプロビジョニングした ESXi ホストを VMware NSX for vSphere 6.1.x のクラスタに追加すると、VXLAN のクラスタ ステータスで次のエラーが表示される：未構成エラー (Error Unconfigure)