Network Interface

Points of interaction between two system. In linux, it's how to OS links up the software side and the hardware side.

Physical interface

Physical port on a device where cables are connected

• Ethernet port
• NIC (Network interface card)

Logical interface

1. VLAN (Virtual Local Area Network) interface:
   • Enable creation of multiple distinct network on the same network switch
2. Loopback interface:
   • Always up and reachable for testing. For example by default is 127.0.0.1 which is commonly used for testing network software
3. Tunnel interface:
   • Used for VPN (Virtual Private Network) tunneling
4. Network Bridge interface
   • Combine all the above into a single interface. Often used in virtualisation and SDN (Software-defined networking)