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Recently I've come across the notion of 'virtual WiFi AP'. For concrete examples of references to this notion, refer to these pointers: 1,2,3.

I'm a bit confused about what virtual APs actually are.

My questions are:

  • What exactly is a virtual AP?
  • Are there multiple ways of implementing a virtual WiFi AP? Which? What do they consist in?
    • For example, I suspect that one way to create virtual APs is configuring the WiFi daemon with multiple SSIDs (e.g. hostapd as explained in this guide).
    • Are there other ways, besides daemon configurations? E.g. based on virtualization, which would allow the state of an AP (e.g. current connections, crypto material like PMKs, etc.) to be 'migrated' between physical devices, like virtual machines?
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What exactly is a virtual AP?

Depends on which vendor or product you are talking about. In general, I would define a virtual AP as a "logical AP" rather than a physical AP device. This may involve providing multiple logical APs on a single physical device or treating multiple physical devices as a single logical AP.

Are there multiple ways of implementing a virtual WiFi AP? Which? What do they consist in?

Yes, there are different ways of creating a "virtual AP." Here are some of the examples of which I am aware (and am by no means confident there aren't more):

  • The ability to run more than one BSSID on a single radio. In other words, the ability to take one physical radio and segment it into multiple WLANs.
  • The ability to run something analogous to a VRF. Take a physical AP device and run multiple independent virtual APs on it. Each AP could be configured differently and even go so far as to talk to a separate controller.
  • Single cell or shared BSSID architecture takes multiple APs and turns them into a single logical AP.
  • One vendor (now acquired by another) had a feature that created a virtual AP per connected client device that can be moved from physical AP to physical AP. This gives a great deal of control to the wireless environment to treat clients differently, but puts a greater strain on the physical AP devices themselves. This would be closest to the last point in your question.

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