[PVE-User] Proxmox VE 7.2 - Problem of understanding 'bridge-disable-mac-learning'

[Stoiko Ivanov]

hi,


On Wed, 4 May 2022 14:10:59 +0200
Martin Dziobek <dziobek at hlrs.de> wrote:

> Dear all,
> 
> In the Release Notes of 7.2, it says:
> 
> "Administrators can now disable MAC learning on a bridge in /etc/network/interfaces with the bridge-disable-mac-learning flag.
> This reduces the number of packets flooded on all ports (for unknown MAC addresses), preventing issues with certain hosting 
> providers (for example, Hetzner), which resulted in the Proxmox VE node getting disconnected"
> 
> where as in descriptions of how to disable mac bridge learning
> for example on  https://www.xmodulo.com/disable-mac-learning-linux-bridge.html
> 
> it says:
> 
> "Once MAC learning is turned off, a Linux bridge will flood every incoming packet to the rest of the ports. 
> Understand this implication before proceeding."
> 
> So flooding is reduced *or* increased ...
> 
> May someone shed a light on this ?
I think the commit message of the relevant commit describes the situation
quite well:
https://git.proxmox.com/?p=pve-common.git;a=commit;h=354ec8dee37d481ebae49b488349a8e932dce736

it disables learning on the individual ports - but at the same time also
the unicast_flood flag is set to false - see `man 8 bridge` - so I'd
expect the combination of the 2 to work as advertised
(and will try to rephrase the release note entry a bit too be less
confusing)

I hope this helps!

Best regards,
stoiko