Hi,

thank You for the answers. 

So to sum up the thread:

There is no drawback or problems with higher MTU *if* the lower level of network equipment can handle this higher MTU. 

For the record (for network guys it is obvious, but it is worth to mention once again):

I confirmed it on our test environment, and all devices in path need to have higher mtu, physical servers, controllers (especially network controllers) and also switches. 

— 

Regards

Lukasz

Yes, we are on the same page. That's why 1500 is the default for that setting.

1500 for VM requires customized setting and proper support from underlay.

Thanks!

Tony 

On Sep 23, 2024 4:11 PM, Jeremy Stanley <fungi@yuggoth.org> wrote:

On 2024-09-23 16:05:40 -0700 (-0700), Tony Liu wrote:
> Default or not, depends on how you see it. 1500 is the most common
> MTU, so that setting is 1500 by default. Makes perfect sense to
> me.
[...]

I think we're talking past one another. The point I was trying to
make is that if you are tunneling the traffic to your guests but
force them to 1500 MTU, things will *break* unless your network
equipment has been configured to handle the additional overhead of
the tunneling, because the tunneling protocol adds outer headers
which will make full-size tunneled packets longer than your Ethernet
frame size and then they won't pass through your switches (or
depending on the tunneling implementation they might simply get
fragmented and then your performance will just be terrible instead).
--
Jeremy Stanley