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Configuring the speed and duplex of an ESX Server host network adapter

Purpose

Configuring the speed and duplex of a network link is important for reliable network operation. This article shows how to configure these parameters on an ESX Server host.

Resolution

ESX recommended settings for Gigabit-Ethernet speed and duplex while connecting to a physical switch port are as following:

  • Auto Negotiate <-> Auto Negotiate
  • 1000 MB /Full Duplex <-> 1000 MB /Full Duplex
  • It is not recommended to mix hard-coded setting with Auto-negotiate.
  • Fast Ethernet – 100 MB /Full Duplex <-> 100 MB /Full Duplex
  • For additional information about Virtual Switch properties, please refer ESX Server 3 configuration guide .
    • Section: Advance Networking>Virtual Switch properties > Editing Virtual Switch properties

    Duplex Mismatch

    • A common issue with speed/duplex is when the duplex settings are mismatched between two switches, between a switch and a router or between the switch and a workstation or server.
    • This can occur when manually hardcoding the speed and duplex or from autonegotiation issues between the two devices.
    See the diagram below:



    The advantages of utilizing AUTO-NEGOTIATION on Gigabit-Ethernet Interfaces:
  • AUTO-NEGOTIATION is highly recommended on ESX Gigabit-Ethernet Interface cards and physical Gig switch ports for the following reasons:
    • Even though hard coding the speed and duplex will work and is in the documentation - In some cases there are performance
      issues after       an ESX upgrade 3.5 – setting the configuration to Auto-negotiate seems to resolve performance issues.
    • It resolves issues with ISCSI, VMOTION, NETWORK PERFORMANCE, and related network issues.
    • Duplex settings—while Cisco devices only support full-duplex, the IEEE 802.3z standard does have support for half-duplex Gigabit-Ethernet.
      Because of this, duplex is negotiated between Gigabit-Ethernet       devices.
    • Flow Control—Because of the amount of traffic that can be generated by Gigabit-Ethernet, there is a PAUSE functionality built into Gigabit-Ethernet.
      The PAUSE frame is a packet that tells the far-end device to       stop the transmission of packets until the sender is able to handle all the traffic and clear its buffers.
      The PAUSE frame has a timer included, which tells the far-end device when to start to send packets again. If that       timer expires without getting another PAUSE frame,
      the far-end device can then send packets again. Flow-       Control is an optional item and must be negotiated. Devices can be capable of sending or responding to a PAUSE frame, and they possibly do not agree to the flow-control request of the far-end.

  • FAST ETHERNET – 100/full <–> 100/full - VMware recommends forcing the network adapter on the ESX Server host and the physical switch port to which
    it connects to 100/Full when using 100 MB links with ESX     Server host.

Configuring the speed and duplex of the ESX Server network adapter using the Virtual Infrastructure Client (VI Client)

To configure the speed and duplex of the ESX Server host network adapter using the VI Client:

  1. Log in to the Virtual Infrastructure Client as the root user or a user with equivalent permissions.

  2. Highlight the ESX server host and click the Configuration tab.

  3. Click the Networking link.

  4. Click Properties next to the appropriate virtual switch.

  5. Click the Network Adapters tab.

  6. Highlight the desired network adapter, and click Edit.
  7. Select appropriate speed and duplex from the dropdown box.
The following ESX command is utilized to configure Network Interface Cards:
  • esxcfg-nics <options> [nic]
The following is a description of esxcfg-nics.The command esxcfg-nics provides information about the Physical NICs in use by the VMkernel.
This will print the VMkernel name for the NIC, its PCI ID, Driver, Link state, Speed, Duplex, and a short PCI description of the card.
It also allows users to set speed and duplex settings for a specific NIC.
 
OPTIONS
 -s --speed speed
Set the speed at which a given card should run. It must be one of 10, 100, 1000, or 10000.
-d --duplex duplex
Set the duplex value which a given card should run.
-a --auto
Set the given NIC to auto-negotiate its speed and duplex settings .
-l --list
List the NICs in the system, and print their current and configured speed and duplex.
-r --restore
Restore NIC settings from persistent storage. This should only be used only on system startup and should not be used by users.
 
Note: For ESX 2.5 and earlier, please see      Setting Network Adapter Speed in ESX Server (813)   .   


Configuring the speed and duplex of the ESX Server host network adapter at the service console


To configure the speed and duplex of the ESX Server host network adapter using the service console:   


    

  1. 

    Log in to the ESX Server host as the root user at the physical console, by remote console, or by SSH.   
    

  2. 

    Type the following command and press Enter to list the available network adapters and their current settings:

    [root@server root]# esxcfg-nics -l   
    Name PCI Driver Link Speed Duplex Description
    vmnic0 04:04.00 tg3 Up 1000Mbps Full BCM5780 Gigabit Ethernet
    vmnic1 04:04.01 tg3 Up 1000Mbps Full BCM5780 Gigabit Ethernet

              
    

  3. 

    The following examples illustrate how to change the speed and duplex of an ESX Server network adapter.

    Configure vmnic1 for autonegotiation:

           [root@server root]# esxcfg-nics -a vmnic1

           Force vmnic1 to operate at 100/Full:
       
    [root@server root]# esxcfg-nics -s 100 -d full vmnic1

    Type    esxcfg-nics without parameters to get full usage information.                    
  


					
					

					
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  • 
									KB Article: 1004089
								
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  • 
									Updated: Aug 14, 2009
								
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  • Products:
     
									
									
									
										VMware ESX
    																		
										
									
										VMware VirtualCenter																		
										
									
								
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  • Product Versions:
     
									
									
									
										VMware ESX 3.0.x
    																		
										
									
										VMware ESX 3.5.x
    																		
										
									
										VMware VirtualCenter 2.0.x
    																		
										
									
										VMware VirtualCenter 2.5.x																		
										
									
								
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