OpenVPN is one type of VPN for the interconnection of local networks that utilize public networks (WAN / Internet) with communications that are secure. VPN is commonly used when required high data security. By default, OpenVPN uses UDP port 1194 and required certificate on each device to be connected. For client compatibility, OpenVPN can be built almost on all Operating Systems with the help of third-party applications. OpenVPN uses an algorithm sha1 and md5 for authentication process, and using some cipher that is blowfish128, AES128, AES192 and AES256. Traffic that passes through the OpenVPN tunnel will have overhead ± 16%.
For example the case, we will try to connect the two networks using OpenVPN. Each network has one main gateway routers.
First, to improve the security of OpenVPN connection, we will add the certificate on the server and client.
Once we make the certificate, we will activate the first OpenVPN server at the main gateway router ‘Office A’. Select menu on the Tab Interface PPP → click on the button Command OVPN Server. And to activate the OpenVPN Server check Enabled option. We also add a certificate for OpenVPN connection in ‘Office A’ as OVPN Server on parameters ‘Certificate’ as the following display.
To further facilitate the setting improvisation, the OpenVPN server we will create a static interface for OpenVPN manually. Actually, if we do not make the interface, the router will make OpenVPN interface is dynamic by the router when the OpenVPN connection is established. However, the interface will be lost if the connection is lost.
/ ip route add distance = 1 dst–address = 172.31.1.0 / 24 gateway = OpenVPN