mtu configuration should not be moved to bridge interface

[Trent Lloyd]

When deploying juju 2.0-beta7 onto a xenial machine managed by MAAS 2, the mtu statement is moved from the interface to the bridge.

The MTU statement must be on the interface to work, as bridges inherit the lowest MTU of all sub-interfaces.

Further to this, ifupdown seems to bug out and always fails to add the default route when an MTU is set on the bridge. Thus, this issue completely breaks the network on reboot.

[Trent Lloyd (lathiat)]

The following bug is partially related, but is technically for a different issue:
https://bugs.launchpad.net/juju-core/+bug/1403955

[Trent Lloyd (lathiat)]

I do not agree duplicate determination. Was it marked duplicate because you plan to effectively fix it at the same time?

My issue is not with what the MTU is set to, but simply that the MTU already there (in my case, placed there by MAAS) was moved from the interface to the bridge stanza. This is both invalid, and also breaks the network bring-up so that you don't get a default route, leaving the state server broken after a reboot.

[Andrew McDermott (frobware)]

I agree that this is not a duplicate of bug #1569802. Plan to fix this for juju-2.0-beta12.

[Andrew McDermott (frobware)]

RB - http://reviews.vapour.ws/r/5234/

[Michael Foord (mfoord)]

1.25 backport : https://github.com/juju/juju/pull/6013