Verifying network links for ESX/ESXi hosts
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Verifying network links for ESX/ESXi hosts

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Article ID: 343872

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Updated On:

Products

VMware vCenter Server VMware vSphere ESXi

Issue/Introduction

This article provides ways to verify that the network links between the physical network adapters and the physical switch of the ESX/ESXi host are up and available for use.

Symptoms:

  • Network failure to ESX/ESXi host
  • Complete or partial network outage
  • Pinging the physical switch fails
  • Connection to ESX/ESXi host is down

Environment

VMware vsphere ESXi 7.0

VMware vsphere ESXi 8.0

Resolution

To verify your network links, perform one or more of the following options:

Check the network link status within the vSphere Client :

  1. Select the ESX/ESXi host and click the Configuration tab.
  2. Select Networking .
  3. The Virtual Network Adapters (vmnics) currently assigned to virtual switches are shown in the diagrams in the client. If one Virtual Network Adapter has a red X over it, it indicates that the link is currently down.

    Note: This can be caused by a misconfiguration of the etherchannel on the physical switch.

Check the status from the ESX/ESXi host:

  1. Run this command:

    [root@server root]# esxcfg-nics -l

    The output appears similar to:

    Name PCI Driver Link Speed Duplex Description
    vmnic0 04:04.00 tg3 Up 1000Mbps Full Broadcom BCM5780 Gigabit Ethernet
    vmnic1 04:04.01 tg3 Up 1000Mbps Full Broadcom BCM5780 Gigabit Ethernet

    Note: To run this command in ESXi, you must enable the SSH service on the ESXi host .To do this on the Host Client select Manage -> Services. Enabled the TSM-SSH service.

    If you are unable to run the command, see Unable to connect to ESXi host using SSH

     
  2. The Link status specifies the status of the link between the network adapter and the physical switch and can be either Up or Down.
  3. If there are several network adapters and some links are up and some links are down, you must verify that the adapters are connected to the intended physical switch ports.
  4. To do this, bring down each of the port of the ESX/ESXi host on the physical switch and then run the esxcfg-nics -l command to see which vmnic is affected..
  5. Utilize Cisco Discovery Protocol (CDP) to discover switch ports corresponding to vmnic connections.

Check NIC link status in Host Client. The following image demonstrates a LINK DOWN status:



Note: If a physical network adapter is missing from the list, verify that it is enabled in the server's BIOS settings. See vendor documentation for more information.

  • Check the status at the physical server's network adapters:

    Observe the LED lights on the physical network adapter. Refer to your network adapter or server's documentation for the meaning of the lights. If no lights are illuminated, this typically indicates a link down state or that the integrated network adapter is disabled in the BIOS settings (if applicable).
     
  • The Admin Status is the only portion of the output that ESXi controls. The link status column specifies the status of the link between the physical network adapter and the physical switch. The link status can be either Up or Down.

    # esxcli network nic up -n vmnicX
    # esxcli network nic down -n vmnicX

    Important: If the Link Status shows the link as down, contact the host hardware vendor for troubleshooting. For more information, see Network adapter (vmnic) is down or fails with a failed criteria code.

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