Problem Case: VLAN tags are not displayed in Wireshark

Introduction

Wireshark is an open-source packet capture tool that anyone can freely install and use on their PC, and is widely used.
I've been running into an issue where when I capture Ethernet FRAMES with VLAN tags using Wireshark, the VLAN tags are not displayed.
In this column, I will talk about the process of solving this problem.

Even if a VLAN tagged Ethernet FRAMES is received, the VLAN tag is not displayed.

In the configuration shown in Figure 1, two PCs are connected via an Ethernet CABLES via SWITCHES, and one PC sends an Ethernet FRAMES with a VLAN attached, which is then received by the other PC via SWITCHES the received Ethernet FRAMES was checked using Wireshark on the receiving PC, it was found that the VLAN tag had disappeared.
Using Wireshark on the sending PC, we were able to confirm that an Ethernet FRAMES with a VLAN tag was being sent. But where on earth did the VLAN tag disappear?
My first suspicion was that SWITCHES might be removing the VLAN tags, so I checked by directly connecting the PCs as shown in Figure 2, but the issue of the VLAN tags disappearing was not resolved.

Could the problem be with the Wireshark settings?

I wondered if the Wireshark settings were causing the VLAN tagged Ethernet FRAMES not to appear on the Wireshark screen even though they were being received properly, so I checked the Wireshark settings, but I couldn't find any such settings. Also, since the Wireshark transmission log properly displayed the VLAN tag, I concluded that this was not a possibility.

Is there a problem with the PC settings?

I was searching the Internet to see if anyone had reported this issue, and I found information that suggested that changing the properties of the PC's Ethernet interface could resolve this issue. Following this information, I changed the "Packet Priority and VLAN" setting to "Packet Priority and VLAN Disabled" as shown in Figure 3, but the issue did not improve.

Could the Ethernet controller be the cause? (Part 1)

I was completely at a loss as to what the cause of this problem was or how to solve it, when I came across information online that said, "Some Ethernet controllers remove the VLAN tag when receiving Ethernet FRAMES." I wondered if this might be the cause, and began researching. I was unable to find any information as to whether the Ethernet controller installed in my PC was this type of controller. I then tried using a PC with a different Ethernet controller, but the problem persisted.
So I decided to look for an Ethernet controller that doesn't strip VLAN tags when receiving Ethernet FRAMES.

Could the Ethernet controller be the cause? (Part 2)

While searching for an Ethernet controller that does not remove VLAN tags when receiving Ethernet FRAMES, I found information that the ASX AX88179 (USB to Ethernet conversion device) is this type of Ethernet controller. I was unable to identify or obtain a PC equipped with this device, so I was at a loss as to what to do next. However, since the AX88179 is a USB to Ethernet conversion device, I thought there might be a USB Ethernet adapter available for sale that incorporates this device. Upon further investigation, I discovered that the AX88179 is incorporated into the Plugable USB 3.0 Gigabit Ethernet Adapter released by Plugable Technologies.
I immediately decided to get this adapter product.

Uses a Plugable USB 3.0 Gigabit Ethernet Adapter

I used a Plugable USB 3.0 Gigabit Ethernet Adapter on the PC receiving the Ethernet FRAMES, as shown in Figure 5, to check whether the VLAN tag would be displayed on the Wireshark screen. Contrary to my expectations, the VLAN tag was not displayed.

Do I need to set the properties of the Ethernet interface? (Solution)

I wondered if the Ethernet interface property settings I mentioned earlier were necessary, so I tried making the same property settings for the Pluggable USB 3.0 Gigabit Ethernet Adapter I was using. As a result, the VLAN tag was displayed on the Wireshark screen as expected.

Summary

In this column, we explained the process for resolving the issue of VLAN tags not being displayed on the Wireshark screen even when VLAN-tagged Ethernet FRAMES were received. We discovered that the cause of this issue was that the PC's Ethernet controller was stripping the VLAN tags from received VLAN-tagged Ethernet FRAMES. One solution is to use a USB 3.0 Gigabit Ethernet adapter that uses an Ethernet controller that does not FRAMES received VLAN-tagged Ethernet frames.
I hope the contents of this column will be helpful if you encounter a similar phenomenon.