Client software choice
The OpenVPN protocol is not one that is built into Macintosh. Therefore a client program is required that can handle capturing the traffic you wish to send through the OpenVPN tunnel, and encrypting it and passing it to the OpenVPN server. And of course, the reverse, to decrypt the return traffic. So a client program is required, and there are some options here. We do not intend to limit our customers and cause a type of vendor lock-in situation. We try to keep connectivity and the choice of client software open, although we do recommend the official OpenVPN Connect Client of course.
Official OpenVPN Connect Client in Access Server
The simplest one, and the one that comes with OpenVPN Access Server itself, is called OpenVPN Connect Client. This program is purposefully limited in its functionality in the sense that it only supports one active VPN tunnel at a time. Trying to connect to two different servers at the same time is a function we did not build into our official OpenVPN Connect Client. And we did so on purpose. Connecting to two servers at the same time means there are two different adjustments made to the routing table on the client computer. It is very easy therefore to make a mistake and break connectivity. Limiting this to one server makes this less likely to go wrong. The OpenVPN Connect Client is able to remember multiple different servers, but only one can be active at a time.
To obtain the OpenVPN Connect Client, log on to your Access Server's web interface (not the /admin portion) and log on with valid credentials. The OpenVPN Connect Client will be offered for download automatically. Download and open it. You may need to ctrl+click it and select 'open' to bypass a security warning. Then install it, and in the system tray (next to the clock on your screen) at the top right, you will see a new orange OpenVPN icon show up. Click it and navigate the menu to find the option to connect to your server, and you'll be asked for credentials, or you'll be connected immediately when you're using an auto-login privileged account. Use the same tray menu to disconnect.
After initial installation you can use the system tray menu to start and stop the connection from now on.
This program is designed to function on Macintosh OS X 10.8 and higher. It may still work on older versions but this is not guaranteed.
OpenVPN open source Tunnelblick program
The open source project has a client for Macintosh operating systems as well. It is called Tunnelblick and it is less limited in functionality than the OpenVPN Connect Client because it does support the option to connect to multiple OpenVPN servers at the same time.
On the other hand, it does miss some features that Connect Client does have as well like Python support for post-auth scripting and other functions that integrate Connect Client with Access Server, like the ability to import connection profiles directly from an Access Server, or the ability to authenticate any valid user on your Access Server and have them connect without having to install a connection profile for each separate user account. This is accomplished on the Connect Client with a universal server-locked profile which is not supported by the OpenVPN GUI program.
This program supports drag and drop to place OpenVPN connection profiles into Tunnelblick. These can be of .conf or .ovpn file extension. You can for example download a user-locked or an auto-login profile from the OpenVPN Access Server web interface, and drag and drop it on the Tunnelblick icon. The tray menu in the system tray will then show you options to use this connection profile - to start or stop the connection. Server-locked profiles are not supported, as mentioned earlier.
This program does support connecting to multiple OpenVPN servers at the same time, but there is a catch. You have to be careful not to implement conflicting routes and subnets when connecting to multiple OpenVPN servers at the same time. Unlike on Windows platform however, you do not need to worry about adding multiple virtual network adapters. These are provisioned automatically.
It can be obtained from the Tunnelblick website.
Viscosity OpenVPN client
Another good OpenvPN client created by an external party, SparkLabs. It is available for Windows and Macintosh. It is compatible with OpenVPN Access Server.
It can be obtained from the SparkLabs Viscosity website.
There are too many to name. There is however a page on the community website that tries to list them all.