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If I am correct, a network interface is the interface between a network interface controller and a network. If I am not correct, please let me know.

  • How many network interface can a network interface controller have? (My guess: one)

  • How many network or MAC address can a network interface have? (My guess: one)

My question is from the fact that a computer or a router can have multiple IP or MAC addresses. Does that mean the computer or router

  • have multiple network interfaces, each of which has an address, or
  • have multiple network interface controllers, each of which has a network interface assigned with an address,
  • or both?

Thanks.

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When most people refer to a Network Interface Controller, they mean a single port. Some people use the acronym, NIC, to refer to this, or to Network Interface Card which may actually have multiple interfaces.

There are corner cases which blur the hard lines you may want to draw. For instance:

Generally, each controller (not card) would control a single interface, but there are things like switches which may use ASICs controlling multiple ports. In such a case, you must consider the "controller" broken into is individual parts, with a PHY on each physical port. Each physical port may still have its own MAC address, but the overall controller could be considered to have multiple MAC addresses.

When you refer to a computer, I assume you mean a PC or end-user workstation. Most PCs have individual controllers for individual physical interfaces, but there are some specialty cards which can be used, in conjunction with software, to turn a PC into a router or switch. Each physical port would still have a MAC address.

The IEEE 802 documents explain all the pieces and parts of the software and physical parts and requirements for controllers and interfaces.

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