Verifying network links

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 5.5
VMware ESX Server 3.5.x
VMware vSphere ESXi 5.1
VMware VirtualCenter 2.5.x
VMware ESXi 3.5.x Embedded
VMware vCenter Server 5.1.x
VMware ESXi 3.5.x Installable
VMware vCenter Server 4.0.x
VMware VirtualCenter 2.0.x
VMware vCenter Server 6.0.x
VMware vSphere ESXi 6.0
VMware vSphere ESXi 6.5
VMware vCenter Server 5.5.x
VMware vCenter Server 6.5.x
VMware ESXi 4.0.x Installable
VMware ESX Server 3.0.x
VMware vSphere ESXi 5.0
VMware ESXi 4.0.x Embedded
VMware vCenter Server 4.1.x
VMware ESXi 4.1.x Embedded
VMware ESX 4.1.x
VMware ESX 4.0.x
VMware vCenter Server 5.0.x
VMware ESXi 4.1.x Installable

Resolution

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

Check the network link status within vSphere/VMware Infrastructure (VI) Client:

1. Highlight the ESX/ESXi host and click the Configuration tab.
2. Click the Networking hyperlink.
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 Tech Support Mode. For more information, see Unable to connect to an ESX host using Secure Shell (SSH) (1003807). For ESXi 4.0 and earlier versions, see Tech Support Mode for Emergency Support (1003677) and for ESXi 4.1 and later versions, see Using Tech Support Mode in ESXi 4.1 and ESXi 5.0 (1017910).
2. The Link column 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 VI 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).
In ESXi 5.0 and 5.1, it is possible to change the link state manually from the command line. To bring a specific vmnic up or down, use the following two commands:

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

Additional Information

Tech Support Mode for Emergency Support
Using Tech Support Mode in ESXi 4.1, ESXi 5.x, and ESXi 6.x
ネットワークリンクの確認
验证网络链接