[systemd-devel] Should `MACAddressPolicy=persistent` for bridges/bonds/all-software-devices be reconsidered?

[Major Hayden]

> 1) for bridge/bond interfaces, there is a special meaning of leaving
> the MAC address unassigned. It causes kernel to automatically set the
> MAC address when the first port gets attached. By setting a persistent
> MAC address, that automatism is not longer possible.

This is incredibly important when using bonded interfaces at cloud
providers that expect only to see known MAC addresses on the network.

For example, at Equinix Metal (formerly packet.net), the switch upstream
from the server expects to see MAC addresses from either of the NICs
attached to the server. If a bond interface MAC doesn't match either of
those two, the network traffic is blocked. This is a common practice for
many cloud providers.

This issue has caused me plenty of headaches until I realized the switch
was eating my traffic coming from an unknown MAC.

--
Major Hayden