Resolution
First of all, you should request a Virtuozzo VPN certificate using the following web form:http://www.parallels.com/en/support/virtuozzo/certificates
After the certificate is received the following steps should be done for configuring VZVPN:
# vzvpn.sh key-install license.vzvpn(replace license.vzvpn with the actual filename) will install your certificate;
# vzvpn.sh startThis command will set up network interface tap0 which will be used by
the support team to connect to your server. When the job is done, use
# vzvpn.sh stopto close the tunnel. OpenVPN uses port 80 for communication, so, please,
make sure this port is open and configure proxy in /etc/vzvpn/vzvpn.conf if needed. You can also use port 443. It can be configured in the same configuration file.