ESXi

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  • 1.  Jumbo frames at the OS level?

    Posted Mar 26, 2013 02:50 AM

    Quick question, I understand jumbo frames need to be enabled end-to-end, but do I need to change it at the OS level too? I mean do I go into the NIC's advanced properties and configure the Jumbo packet there too or is configuring at the vSwitch level enough? It would seem to me that it wouldnt hurt. I'd have tested this but I'm at a customer's premises and cannot test.

    Help's appreciated!



  • 2.  RE: Jumbo frames at the OS level?

    Broadcom Employee
    Posted Mar 26, 2013 09:15 AM

    Hi,

        Are your doing some sort of I/O test?

    1)Jumbo frames allow ESXi to send larger frames out onto the physical network. The network must support jumbo frames end-to-end.

    2)Jumbo frames up to 9kB (9000 bytes) are supported.

    3)Enabling jumbo frame support on a virtual machine requires an enhanced vmxnet adapter for that virtual machine(If not, remove and re-add the network interface ensuring enhanced vmxnet is selected)

    1. Log in to the guest virtual machine.
    2. Right-click My Network Places and click  Properties.
    3. Right-click the network adapter and click Properties.
    4. Click Configure.
    5. Click the Advanced tab and change the MTU value.
    6. Click OK to apply the changes.


    1. 3.  RE: Jumbo frames at the OS level?

      Posted Mar 26, 2013 09:57 PM

      Thanks for taking the time to reply, I know how to configure jumbo frames at the OS level. I guess the question is - do I need to? If I jumbo-frame the vSwitch and the rest of the network, do I need to do the OS layer too?



    2. 4.  RE: Jumbo frames at the OS level?
      Best Answer

      Posted Mar 26, 2013 10:01 PM

      If somewhere in the whole patern there are no jumbo frames, everything will go back to the standard MTU (1500). If you have a reason why you would need jumbo frames on the OS then you'll have to configure it. This is usually if a customer wants it or for a specific app.

      If you are using iSCSI storage it is usually suggested to use Jumbo frames as well.



    3. 5.  RE: Jumbo frames at the OS level?

      Posted Mar 26, 2013 10:12 PM

      Right, that's what I was after. And yes, I realize VMware recommend jumbo frames for iSCSI if the network supports it, this customer of mine uses them.

      Thanks!



    4. 6.  RE: Jumbo frames at the OS level?

      Posted Mar 27, 2013 02:15 PM

      Niels Engelen wrote:

      If somewhere in the whole patern there are no jumbo frames, everything will go back to the standard MTU (1500).

      A somewhat important detail in my opinion is that if any of the end stations do not support jumbo frames then they negotiate to the default 1500 Byte MTU. However, if any layer two device in between (virtual or physical switch) does not support it then this will be invisible to the end stations and makes the large frames get silently dropped and large connectivity errors as result.



    5. 7.  RE: Jumbo frames at the OS level?

      Posted Mar 27, 2013 11:11 PM

      That IS an important detail Rick. I've seen that myself happen a customer's infrastructure.

      Thanks for the reminder!



    6. 8.  RE: Jumbo frames at the OS level?

      Broadcom Employee
      Posted Mar 27, 2013 01:20 AM

      Hi,

          Ideally not required to configure in Guest O/S.If there is a specific need for that,go for it with the Supported NIC.Just you need to configure it end to end.If your clients connect to the server (Guest) it is possible they do not accept frames above an MTU of 1500 ? That packet will be dropped and getting framentated.So be carefull with activating jumboframes in Guest O/S.