thank you for the fast feedback and the explanations 
Is it possible to have version hint somewhere on the documentation?
or even better: generate the documentation for all versions:
- https://linuxcontainers.org/lxc/manpages/v2.1/man5/lxc.container.conf.5.html
- https://linuxcontainers.org/lxc/manpages/v2.0/man5/lxc.container.conf.5.html
- etc
edit: it would be also good to have the latest “stable” documentation as default
edit2: tried man lxc.container.conf on Debian 8 with lxc 2.0.7.
There is no hint for the network indexes with [i] - but it’s working?