Comment 3 for bug 1567440

Hmm, the fact that you had lxcbr0 was probably a bug in a previous migration script, it should have been lxdbr0.

We can't use lxcbr0 because on most systems lxc1 will be marked for auto-removal after upgrading to the lxd version which brings lxdbr0, so at configuration time the bridge would still be there, but 10min later, not so much.

We also can't default on any subnet, that's the whole point of lxdbr0, defaulting on a subnet has been breaking user network in the past and is exactly why we were told not to do that anymore. We do suggest a subnet in all those questions though, typing in those values will get you working networking.