I recently setup a new Ubuntu server with LXC containers. At first it all went great, but then
later when I enabled UFW, things got flaky. Looking at
/var/log/syslog I saw UFW was blocking
lots of traffic from inside the containers.
Also when restarting a container, the container wouldn't get one of the bridged
10.x.x.x IP addresses.
After Googling a bit, I found the magic commmands on this discussion:
ufw allow in on lxdbr0 ufw route allow in on lxdbr0
In hindsight, I think it would have been better to enable
ufw before doing anything else with the new install,
that way the problems would have been more obvious right away - rather than it being a "geez, it was working before"