It's usually bad to mix tagged & untagged traffic on the same port, but mixing traffic across multiple ports on the same VLAN should be fine, right?
Apologies for posting three images as one: new users cannot post multiple images
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The first VLAN Bridge Filtering configuration works properly. Lan1 provides connectivity to multiple switches across a Devolo powerline, and those switches separate out VLAN traffic correctly. Note that vlan10 is untagged on extsw, and this functions as expected (see below).
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But when I try to connect a machine directly to lan4 on vlan20 (middle image), although that machine has untagged connectivity, it breaks tagged connectivity to vlan20 on lan1.
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The only workaround I've found (third image) is to set lan4 as a tagged port and the primary vlan ID, but I don't think this is satisfactory because it effectively mixes tagged and untagged traffic on the same port, which we already know is bad.
This is an Asus RT-AC88U (HW: ?) running 22.03.02, because there's currently an issue with the latest versions. The AC88U has 8 ports of which WAN + 1-4 are Broadcom and 5-8 are Realtek (extsw); this may be relevant.
The Realtek switch seems to accept both tagged and untagged ports over the same VLAN but the four ports cannot be separated; the Broadcom switch allows for individual configuration but seems to have issues with this kind of mixed mode.
I'm a recent convert from DD-WRT and previously had issues getting VLANs to work as a single subnet over both wired and wireless, which was blamed on Broadcom. I suspect there is an issue here with the Broadcom (closed source?) drivers.
- Is this likely to be Broadcom related?
- Are there any known workarounds?
- Am I right not to want to allow tagged and untagged traffic on lan4?