I have disabled 802.1Q module in my Cento 7 VM and did arping through one of the interface to it's gateway IP and captured packet traffic on that interface from the same VM.

[root@vm1 ~]# lsmod | grep 8021q
8021q                  33208  0
garp                   14384  1 8021q
mrp                    18542  1 8021q
[root@vm1 ~]# modprobe -r 8021q
[root@vm1 ~]# lsmod | grep 8021q

My expectation was that exgress packets wouldn't have any VLAN tags. The machine I pinged is the windows host and also VLAN tags support was not added in the windows host. So, I also expect that the ingress packets also won't be having any VLAN tags.

But I see VLAN tag with default ID: 1 on both the packets.

So, is the module 8021.q in Centos 7 is obselete and not needed at all?

enter image description here

Edit 1:

I checked again by analyzing ping traffic. For ping, there is no VLAN tag ids added (with and without 8021q module loaded)

enter image description here


Issue is with the decoding type I have selected. I selected decoding as VLAN for link and then selected decoding as do not decode. Thus somehow ended up with the above wrong decoding.

I just need to clear decoding to see the actual data and the VLAN tag is then added only when the 8021q module is loaded + when a VLAN tagged interface is created.

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