http://www.freebsddiary.org/openvpn.php
The solution here is rather simplistic. It allows for a single client to
connect to a single server. You cannot do multiple clients with this setup.


http://www.freebsddiary.org/openvpn-easy-rsa.php
The FreeBSD Port for OpenVPN installs "a small RSA key management package based
on the openssl command line tool". This package is provided by the OpenVPN
project and can be found at /usr/local/share/doc/openvpn/easy-rsa/. 


http://www.freebsddiary.org/openvpn-routed.php
In this article, I will show you how I created a routed VPN using OpenVPN. In
this network, multiple clients can attach to the server, each of which has
access to the network attached to the server. Each client can also contact any
other client, subject to firewall rules. 

Revoke/Unrevoke a client certificate in OpenVPN
http://blog.abhijeetr.com/2012/06/revokeunrevoke-client-certificate-in.html

cname is the one which you want to disable:
./revoke-all cname

edit the server.conf & add the following line:
crl-verify crl.pem

ovpnCNcheck — an OpenVPN tls-verify script
http://robert.penz.name/21/ovpncncheck-an-openvpn-tls-verify-script/
http://robert.penz.name/wp-content/uploads/2008/01/ovpncncheck.sh