cakemaker wroteRegarding to the recent post "TAP Driver Install Problem in 2.1.2 - KNOWN ISSUE" by ecrist, I would like to check the version of tap on my centos.
As ecrist already stated, this is a Windows specific issue. OpenVPN only ships TUN/TAP driver for Windows
[1]. For *BSD and Linux, OpenVPN makes use of the native TUN/TAP driver in the OS kernel. So for CentOS, that will be the tun.ko kernel module.
[1] It might be a similar situation for Solaris, but that's unclear for me right now.