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I've got a wireless access point (TP Link TL-WA801ND). The AP has a Multi-SSID mode where the AP will broadcast multiple SSIDs, and optionally VLAN tag the traffic on each of the wireless networks.

The LAN section for that same AP has a single section for setting up IP address and gateway.

If I enable Multi-SSID mode, traffic will then be tagged for a VLAN. However, it appears to me that all traffic still will travel on the same subnet - the one I set up in the LAN section. I can't really get my head around how VLAN separation takes place here.

Even though all traffic from the AP is VLAN tagged, how will this work when - apparently - all traffic still travels on the same subnet?

I do know that I need a switch which supports VLAN tagging, but still - does this change the fact that all traffic apparently will travel on the same subnet?

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2 Answers 2

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From the manual I found this:

"VLAN ID (1-4) - Provide a number between 1 and 4095 for VLAN. This will cause the device to send packets with VLAN tags. The switch connecting with the device must support VLAN IEEE802.1Q frames. The wireless stations connecting to the SSID of a specified VLAN ID can communicate with the PC connecting to the port with the same VLAN ID on the Switch."

In your example above you do use the default vlan (see "VLAN ID: 1"), which is always untagged by definition on how VLAN works.

Besides needing to have switch that supports 802.1Q you will also need a router that supports 802.1Q, since the idea is that you have a trunk link between access point and switch (and also a trunk link between router and switch).

What you are aiming for is having a dedicated subnet per VLAN ID.

Like VLAN ID 1 resides on 192.168.1.0/24 and VLAN ID 2 resides on 192.168.2.0/24 or whatever IP address scheme you might use.

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  • Thanks! I assume this then will implicitly work with the DHCP server configured for the different VLAN's then? That is, the AP will tag DHCP requests with the applicable VLAN ID for the given SSID?
    – sbrattla
    Oct 29, 2019 at 10:14
  • Well if the DHCP server does not reside on the same VLAN ID it wont be able to hand out any IP addresses. However: I have heard about examples where you setup a Raspberry Pi to act as a 802.1Q router. You could install a DHCP server on the same device and thereby handout IP addresses to each VLAN in your network.
    – Lasse Michael Mølgaard
    Oct 29, 2019 at 10:19
  • Yes, I was thinking of using excactly a Raspberry Pi to handle DHCP on the subnets as the router isn't very capable of this. Thanks for your insight!
    – sbrattla
    Oct 29, 2019 at 10:26
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    An example of a debian machine connected to the switch via trunk link: microhowto.info/howto/…, after that the challenge is only about which (VLAN) interfaces should the DHCP server hand out IP addresses.
    – Lasse Michael Mølgaard
    Oct 29, 2019 at 10:29
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Much like a switch (L2), a wireless access point technically does not need to have any IP address (or subnet) at all.

If it doesn't have any other functionality beyond being just an access point, it's very possible that these IP settings are purely for management purposes (ie, which address you connect to in order to use the management UI that you have screenshots from).

Using VLANs as per the screenshot, you would indeed need a VLAN-capable switch and either patching multiple ports to a router or a VLAN-capable router.

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  • I see, and I assume that I should probably have a "default" VLAN then which I can use to access the switch for management?
    – sbrattla
    Oct 29, 2019 at 7:23
  • @sbrattla Not entirely sure what to make of this question specifically about the switch, but it would probably be a good idea to have a separate VLAN for management purposes. How that would work with this AP is unclear at best, though. I opened the manual for your device and that raised more questions than it answered; for one thing it apparently has a DHCP server, so it's some kind of hybrid device. I suppose this is just the curse of consumer-oriented gear.
    – Håkan Lindqvist
    Oct 29, 2019 at 8:29
  • Thanks for your input, and I'm glad to hear I'm not the only one who is a little confused over the combination of VLAN tagging, LAN setup and DHCP operation.
    – sbrattla
    Oct 29, 2019 at 9:33

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