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Can someone explain the concept of the terms interface, device and wireless in OpenWrt?

  • What is their purpose?
  • What is their relation?
  • How do they play together
  • Why are some devices greyed out?
  • The router has wifi capabilities; Why can't I choose wlan0 as a device for an interface?
  • Why can I choose wireless interfaces as devices for interfaces?
  • What does the Network setting do in wireless? What relationship is formed here?
  • Why can only have the default br-lan device have extended DHCP settings?
    • br-lan: DHCP settings of br-lan
    • other devices: DHCP settings of other devices

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Roughly:

  • An OpenWrt device is a network interface in the host Linux operating system (what you see with ip link list). These include network ports, as well as virtual devices like the br-lan bridge.
  • An OpenWrt radio ("wireless") is a device with wireless capability. Every radio provides a device for you to put IP config on, but it also provides a radio object to adjust the many wireless-specific things that wired hardware doesn't have. The UI forces interface configuration into the "Wireless" page. I would guess this is because wireless interfaces are usually bridged (to Ethernet devices), and this lets them put a UI layer in front of the wireless interface to reduce confusion.
  • An OpenWrt interface is an IP address configured on a device or radio, and maybe additional IP-and-higher-layer protocols bound to it.

So if you want to adjust IP addresses or protocols or that kind of thing, you work with interfaces. If you want to adjust MTU or MAC addresses, you work with devices. If you want to set SSID or encryption, you work with radios.

I believe the DHCP UI behavior you are seeing is because only that one interface has a DHCP server running on it.

The "Network" field of a wireless interface (Network -> Wireless -> [your SSID] -> Edit -> Interface Configuration -> General Setup -> Network) lets you pick the OpenWrt interfaces the wireless interface is bridged to.

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    Thank you for your answer! Could you follow up on this one: What does the Network setting do in wireless? What relationship is formed here?
    – DarkTrick
    Commented May 3, 2022 at 21:04
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    @DarkTrick: I've added some commentary on the "Network" field I think you're talking about. If you consider your question resolved, please accept the answer. If you need further help, please refine your question to clarify scope, or open a new question.
    – Ben Scott
    Commented May 3, 2022 at 21:30

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