[pve-devel] Process to submit patches

Andrew Thrift andrew at networklabs.co.nz
Thu Apr 18 06:46:34 CEST 2013

Hi Dietmar,

It depends on what size frame you are trying to pass.  Anything over 
1504 bytes is considered "Jumbo".  An MTU of 9000 would allow you to 
pass a 9004byte frame.  If you were doing "jumbo" frames to one of your 
VM's and wanted double tagging you would set your physical interface 
with an MTU of 9004 to allow for a 9008byte frame.

On 4/18/2013 4:19 PM, Dietmar Maurer wrote:
>> Linux does not clearly differentiate between L2 (interface) and L3 (IP) MTU, and
>> also has a hidden 4 byte allowance on the interface MTU, making it confusing.
>> When running QinQ the parent physical interface needs a MTU of at least 1504
>> bytes (allows a 1508 byte frame), any sub vlan's and bridges will then inherit this
>> MTU allowing for the "inner" tag to pass externally correctly.
> And what are the correct settings for jumbo frames (MTU 9000)?

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