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Multiple untagged VLAN-IDs on one switch-port

Michael Rocholl 0 Reputation points
2023-07-26T15:41:57.5833333+00:00

I want to span two different WLANs (based on Ubiquity-APs) both using the guest port of a Fritz!Box. Let's say these VLANs have ID 200 and 300.

I am using a VLAN enabled switch (Netgear GS324TP) and defined the port which connects to the guest port of the Fritz!Box as "untagged" for ID 200 and 300.

I read that "one should never have a port with more than one untagged IDs" but it works. Devices connecting to both VLANs have Internet access!?

Is this by coincidence or as designed? are there any articles covering this special case?

Many thanks - Michael

Windows Network
Windows Network
Windows: A family of Microsoft operating systems that run across personal computers, tablets, laptops, phones, internet of things devices, self-contained mixed reality headsets, large collaboration screens, and other devices.Network: A group of devices that communicate either wirelessly or via a physical connection.
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  1. Anonymous
    2023-12-21T01:51:45.5133333+00:00

    Hello,

    Thank you for posting in Q&A forum.

    It's not a recommended practice to have a port with more than one untagged VLAN in a VLAN-configured network. Each VLAN should have its own untagged port to make proper isolation.

    In your case, it works maybe because the devices connected to that port could consider all incoming traffic as untagged, regardless of the VLAN tag. This behavior can vary depending on the device and its network stack.

    I will recommend you check with your network device vendor for further details and you might also find related documentations on their website.

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