Wireless only network in 21.02 - is that a vlan?


First my hardware is Xiaomi r3g under 21.02.2.

When I am creating a guest only wireless (no RJ45 physical devices) and attaching that to an interface.
Does that create an internal vlan?

It seems the default configuration created br-lan and wan do not have a vlan.
How does that work exactly?

Before in v18 I used to create all the vlans I needs and attaching those to the wireless I needed.
Now it seems like the new DSA architecture seems a bit confusing.

Thank you

This is potentially a subject of debate.... there is certainly nuance with language here. (and I could be wrong about how I will define things here):

In casual usage, VLANs will refer to any situation with multiple networks/subnets in an overall network topology. In this context, your guest wifi example would be called a VLAN. Similarly, if you have a router that has individually routed ports (and not a switch) such as the ER-Lite, ER-4, etc. -- you could put a different network on each of the ports and say that you have multiple VLANs.

When using precise language, however, if you have multiple networks configured, but only one per routed interface/radio, it is technically just multiple networks/subnets, and not VLANs.

VLANs are a special form of having multiple networks (subnets) in a system. But, specifically, VLANs refer to the situation where multiple networks traverse the a shared data channel/link/fabric by means of tagging one or more networks following the 802.1q standard*. An obvious example of this would be carrying multiple networks over a single cable (i.e. a trunk) between a router and managed switch or VLAN aware AP. A slightly less obvious example would be the connection between the SoC and the internal switch (for all-in-one routers or devices like the ER-X series that have integrated switches). In this case, the shared channel is the internal connection, even if the ports are all configured as access ports (i.e. a single untagged network), almost as if they were individually routed ports.

*it could be argued that VLANs don't necessarily have to take the form of 802.1q standard when the data is flowing internally within a system -- a managed switch, for example, only needs to deal with 802.1q tags on the input/output (i.e. at the ports), but it could use other methods to identify the network to which ethernet frames belong when switching on the internal fabric.

When it comes to DSA, this generally only applies to devices that have built-in switches. Most single-port or routed-port devices do not use DSA syntax, although there are some exceptions (apparently the U6 APs use DSA -- maybe they actually do contain a switch despite just a single ethernet port for the Lite and LR models(?)). Your Xiaomi router does have a built-in switch, so DSA makes sense here, for sure.

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Thank you very much for the explanation.

I read the docs and was not sure on how to address this.
Coming from a Cisco background I found the terminology a bit confusing.

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