Backend for authentication¶
One or more authentication servers to use when checking user credentials. This can be the Local Database (user manager) or it can be a RADIUS or LDAP server configured in the user manager.
Selecting multiple entries will use each one in turn. If authentication against an entry fails, the VPN will try the next server. It will continue this process until it has tried all selected entries.
This field is only present when using a Server Mode which requires user authentication.
OpenVPN can run in one of two device modes: tun or tap:
Works on OSI layer 3 and performs routing on point-to-point interfaces.
Can work at OSI layer 2 and can perform both routing and bridging if necessary.
Not all clients support tap mode. Clients such as those found on Android and iOS only support tun mode in the apps most people can use. Some Android and iOS OpenVPN apps that require rooting or jailbreaking a device do support tap, but the consequences of doing so can be a bit too high for most users.