Verifying network links for ESXi hosts
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Verifying network links for 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 used by an ESXi host and the physical switch are up and available for use.

  • Network failure to ESXi host
  • Complete or partial network outage
  • Pinging the physical switch fails
  • Connection to the ESXi host is down
  • Host is showing as "not responding" in vCenter

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

    Note: This can also be caused by a misconfiguration of a port channel configured on the physical switch.

Check the status from the ESXi host:

  1. Run this command:

    # esxcli network nic list

    The output appears similar to:

    Name    PCI Device    Driver    Admin Status  Link Status  Speed  Duplex  MAC Address         MTU  Description
    ------  ------------  --------  ------------  -----------  -----  ------  -----------------  ----  -----------
    vmnic0  0000:0b:00.0  nvmxnet3  Up            Up           10000  Full    ##:##:##:##:##:##  9000  VMware Inc. vmxnet3 Virtual Ethernet Controller
    vmnic1  0000:13:00.0  nvmxnet3  Up            Up           10000  Full    ##:##:##:##:##:##  9000  VMware Inc. vmxnet3 Virtual Ethernet Controller

    Note: To run this command in ESXi, you must enable the SSH service on the ESXi host .To do this from vCenter, navigate to the host -> Configure -> System -> Services and start SSH. To do so from the host web UI, select Manage -> Services and enable the TSM-SSH service.
     
  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.

    Note: This link state is reported by the driver, and unless the "Admin Status" is also listed as "Down" this almost always refers to a configuration or issue in the physical network, outside of ESXI. See Network adapter (vmnic) is down or fails with a Failed Criteria Code for more information.
     
  3. The "Admin Status" is the only part that the ESXi operating system controls. If this is shown as down you can flap the NIC using the following command (replacing vmnicX with the NIC to modify, for example vmnic0):

    # esxcli network nic down -n vmnicX

  4. 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.
  5. To do this, bring down each of the port of the ESXi host on the physical switch and then run the esxcli network nic list command to see which vmnic is affected.
  6. Alternatively, utilize Cisco Discovery Protocol (CDP) or Link Layer Discovery Protocol (LLDP) 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 and Network cards not detected on an ESXi host 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).

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