I cannot succeed in entering a QinQ number in the "0x8100 0x" field.
I always get "Error: VLAN QinQ field".
You have to enter 4 bytes. This for bytes specify the whole VLAN QinQ tag. It means first seven bits go fro the priority, next bit for CFI and last 12 bits for VLAN ID. That means if you want to enter VLAN ID 100:
100 in hex is 0x64, you have to enter 0064 in this field.
If you want also that priority is set to 5 it gets a little bit more complicated.
5 put into binary is 101, but you have to left shift it once because of the CFI bit. Because this bit is normally 0 you get in binary:
00001010 and in hex this is 0xA
So it means, that for priority 5 and vlan id 100 you enter in packETH QinQ field: A064
If you play with packETH in check the resulsts immediately in Ethereal/Wireshark, you will soon see how it works.
It is wrong what I said in the first sentence.
You don't have to enter 4 bytes but for hex characters. These are actually 2 bytes.
Oh, my english.
for means four (4)