One network optimization that we can configure on Hyper-V are the Jumbo Frames. Although we can take benefit of Jumbo Frames on different scenarios the most common use is to optimize iSCSI network traffic. This traffic is often used to connect the Hyper-V hosts to the SANs but can also be used to connect SAN LUNs directly to the VMs (Passthrought disks).Depending on your scenario you will need to configure the above parameters on the Hyper-V host, inside the VMs or at both levels.

The table below is focused on Intel and Broadcom network adapters but maybe you will need to speak with your vendor if you are using other NIC models. The first setting defines the maximum MTU packet size at OS level on the specified NIC and is 1500 by default. The second setting is to enable Jumbo Frames at NIC driver level and each vendor have their own configuration. You will find specific information for each vendor on the listed links inside the table.

Note that Jumbo Frames feature inside VMs was introduced with Hyper-V R2. Don’t try to find or enable Jumbo Frames feature inside Hyper-V v1 VMs because will not be available.

Finally remember to validate that Jumbo Frames are enabled and working on the SAN, on the physical switch, at OS Level (first setting from the table) and at NIC level (second setting from the table).

You can find more information about MTU on the following document:

TCP/IP Registry Values for Microsoft Windows Vista and Windows Server 2008
http://www.microsoft.com/downloads/details.aspx?familyid=12AC9780-17B5-480C-AEF7-5C0BDE9060B0&displaylang=en

 

Jumbo Frames

NIC adapter Level feature

Collector Script = AdvancedNet_Features.ps1

THIS SETTING MUST BE CONFIGURED ON PARENT PARTITION and/or INSIDE VMs

 

Command to validate MTU config:

netsh int ipv4 sh int

 

Command to change MTU config:

netsh interface ipv4 set subinterface "Local Area Connection X" mtu=9000 store=persistent

(the MTU value is 9000 in this example but can be different based on your needs)

 

THESE REGISTRY KEYS MUST BE CONFIGURED ON PARENT PARTITION and/or INSIDE VMs

 

Registry Key for Broadcom NICs

 "\SYSTEM\CurrentControlSet\Control\Class

\{4D36E972-E325-11CE-BFC1-08002BE10318}\xxxx\*JumboMTU"

 

Broadcom Jumbo frames Settings

 

Registry Key for Intel NICs

"\SYSTEM\CurrentControlSet\Control\Class

\{4D36E972-E325-11CE-BFC1-08002BE10318}\xxxx\*JumboPacket"

 

Intel Jumbo Packet settings