The problem is that there are no ifcfg-vnetX config files. They are
dynamically created as VMs are created or migrated to a node. You could
manually (or via script) change the MTU, but that would mean that the
MTU on the bridge would drop momentarily when new VMs start. This could
break network traffic for any existing VMs (or real devices) using large
frames.
I'm not a fan of udev either, but in this case, it is the best option.
Of course, I am certainly open to hearing alternative methods if they exist.
On 21/11/13 08:39, Nico Kadel-Garcia wrote:
> Stay out of udev if you can. It's often overwritten by component
> addition and manipulation MTU is parsed, and overridden, by options in
> /etc/sysconfig/network-scripts/ifcfg-[device]. I find it much safer to
> read and manage there, and if new devices are added or replaced, the
> behavior is dominated by the "HWADDR" associated config files there,
> no matter what "udev" thinks the device number or name should be..
<snip>
>>
>> Another update;
>>
>> To make sure the VMs' vnetX devices are created with a larger MTU, you
>> *sill* need to update udev[1].
>>
>> Append to /etc/udev/rules.d/70-persistent-net.rules;
>>
>> ====
>> # Make all VMs' vnetX devices come up with an MTU of 9000.
>> SUBSYSTEM=="net", ACTION=="add", KERNEL=="vnet*", ATTR{mtu}="9000"
>> ====
>>
>> Assuming you find that you can use an MTU of '9000', of course. No
>> need to reboot or even restart networking. Just add that line and then
>> provision/boot your VMs. If the VMs are already running, you can adjust
>> the MTU of the existing 'vnetX' devices with:
>>
>> ifconfig vnetX mtu 9000
>>
>> Cheers!
>>
>> PS - Credit for the udev rule:
>>
>> http://linuxaleph.blogspot.ca/2013/01/how-to-network-jumbo-frames-to-kvm-guest.html
>>
>> --
>> Digimer
>> Papers and Projects: https://alteeve.ca/w/
>> What if the cure for cancer is trapped in the mind of a person without
>> access to education?
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--
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?
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