TUN (namely network TUNnel) simulates a network layer device and it operates with layer 3 packets like IP packets. TAP (namely network tap) simulates a link layer device and it operates with layer 2 packets like Ethernet frames. TUN is used with routing, while TAP is used for creating a network bridge.
Packets sent by an operating system via a TUN/TAP device are delivered to a user-space program which attaches itself to the device. A user-space program may also pass packets into a TUN/TAP device. In this case TUN/TAP device delivers (or "injects") these packets to the operating-system network stack thus emulating their reception from an external source.
TUN/TAP is not enabled by default on your VPS. However, you can enable it yourself manually via your SolusVM. You can follow the below instructions to enable TUN/TAP support.
1) Login to your SolusVM VPS account.
2) Select the VPS that you wish to enable TUN/TAP support for by clicking on the Manage button.
3) Click on Settings under Controls.
4) Click on the Enable TUN/TAP button.
To verify that TUN/TAP support has been enabled properly, you can run the below command in SSH. The output you should receive is also shown.
# cat /dev/net/tun
cat: /dev/net/tun: File descriptor in bad state