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MTU 9000

To increase throughput and performance, it is recommended to use MTU 9000 instead of the default MTU 1500. In order to use MTU 9000, all network switching and routing elements between the SoftNAS® VM and the client device must support MTU 9000.

For MTU 9000 to work properly, it must be configured on all physical switch ports, routers, host servers and virtual switches (and within SoftNAS® network interfaces). Be sure to verify networking paths and hosts end to end in order to use MTU 9000 (or it can actually reduce performance and potentially cause packet loss or retries if not configured properly).

EC2 Users - Due to the specific ways in which physical servers and networking infrastructure are configured, some of the physical hosts support jumbo frames, and others do not. On physical hosts that support jumbo frames, AWS documentation states support of Jumbo Frames on all current generation instances but still recommends using caution for internet-bound traffic or any traffic that leaves a VPC.  For additional insight, please refer to Network maximum transmission unit (MTU) for your EC2 instance.


For example: 

SoftNAS VM, eth1 <=> vSwitch <=> VM host physical NIC <=> Physical switch ports <=> VM host 2 NIC <=> vSwitch 2 <=> Client VM

For MTU 9000 to work, all virtual and physical switch ports must be configured for MTU 9000, as well as the virtual machine client's (or VMkernels, if client is running on VMDK).


Within SoftNAS®, to configure MTU 9000 to be persistent upon reboot, simply follow the steps given below:

  1. Log on to SoftNAS StorageCenter.

  2. In the Left Navigation Pane, select the Network Settings option under the Settings section.
    The Network Settings panel will be displayed. Configure and manage all network configuration from here. 

  • Click the Network Interfaces icon.

The Network Interfaces section of the panel will be displayed. 

  • Click the Activated at Boot tab.

  • Select the network interface (eth1) in the list of the interfaces.
    The Edit Bootup Interface section of the panel will be displayed. 
  • In the MTU field, change the value from default to 9000. In order to do so, check the option for the text entry box and enter the value 9000 in the text box.
  • Click Save and Apply.


  • Back in the Network Interfaces panel, click the Active Now tab.
  • Select the interface name (eth1).

  • The Edit Active Interface section of the panel will be displayed.
  • In the MTU field, enter the value as 9000 in the text entry box. This will change the current network interface value to MTU 9000. Be sure that all switching paths are configured to support MTU 9000 before making this change (or risk losing connectivity).
  • Click Save. 

Configuring VMware vSphere for MTU 9000

Before enabling jumbo frames, ensure the following are true:

  • The physical server's network interface card and network switch can support jumbo frames (MTU 9000)
  • The switch ports of all routers and switches between SoftNAS® and VMware vSphere hosts are properly configured for MTU 9000.


VMWare ESX/ESXi supports frames up to 9 KiB (MTU 9000).

In order to use jumbo frames support configuration is required end to end.

These commands are good for ESX/ESXi 5.0 and later:

  1. Log into host with the VMware vSphere client.
  2. Select the physical host to make changes to and click on the host IP.
  3. Choose the Configuration tab.
  4. Select the Networking option under Hardware.
  5. Select properties on the vSwitch to be configured.
    When the vSwitch is selected, the MTU set will become visible under Advanced.
  6. Set Properties. The default is 1500.
  7. Click Edit on the bottom while the vSwitch is selected.
  8. On the General tab there is a box labeled Advanced Properties
  9. Change the MTU here from 1500 to 9000 and click OK.
  10. Also change the MTU for the VMK (VM kernel).
    In the same vSwitch Properties box select the first VMK listed.
  11. The MAC address and MTU are listed under NIC Settings.
  12. Click Edit for the first VMK.
  13. On the properties dialogue box that pops up set the MTU in the NIC settings box on the General tab to 9000 and click OK.
  14. Repeat this for all VMKs under the virtual switch.
  15. Close the vSwitch properties dialogue and repeat for any remaining vSwitches. 

Be sure to set the SoftNAS® network interface to accept Jumbo Frames / MTU 9000, as described above.

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