So … as I could not recover nor recreate the containers as they worked at first time, had to find another solution.
Virtual MAC’s:
Did not worked added with:
lxc config device set mycontainer eth0 hwaddr a:new:mac:address
neither:
lxc config set mycontainer volatile.eth0.hwaddr
(as worked first time).
So I deleted virtual MAC addresses at OVH’s (provider) user panel.
The solution is picked up from several posts:
created virtual bridge for inner communication betwen host and containers
also added (bought) public IP addresses to containers