Actually . . .
"No! ... Absolutely not!" 
"The various participants in your OpenVPN network," including both the servers
and any-and-all clients who are connected
directly to them, necessarily must have a private-to-them range of IP-addresses through which they can communicate
among themselves, without any conflict against any
(client ...) address-range whose communications they might be passing from here to there.
Typically, this agreed-upon address range is
(say ...) 10.8.0.x.
The OpenVPN server carves-out a couple of these addresses for itself, then doles-out other ones both for "other servers" and for directly-connected machines who are running OpenVPN-client software directly.
"The
10.8.0.x subnet," therefore, is "a subnet that OpenVPN reserves unto itself," trusting that no other 'private subnet' anywhere on Planet Earth would
dare(!) to conflict with its sovereign addresses. OpenVPN expects to be able to use these addresses to communicate directly among the various other OpenVPN clients/servers in its present network, as well as the various clients who are
directly connected to any of them.
(If your machine happens to host more-than-one OpenVPN process, then ".8" might turn out to be a sequentially-larger number ... but, I digress.™)
- - -
"And of course, this is merely the usual TCP/IP Routing™ use-case . . ."
