How To Capture Packets With VLAN Tag
Required: 2 PCs/Laptops, a switch (VLAN supported) and wireshark
Diagram:
You may find simpler way to do it in somewhere else’s blog (e.g. packetLife) but my idea comes the characteristic of broadcast. That is the broadcast will send out to everywhere in the broadcast domain including ports which are in TRUNK mode on the same switch. Configuration is simple as suggested in the diagram. And I just send a ping to 10.10.10.255 from PC1 which is in the same network or VLAN and the wireshark running on the PC2 which is connected to the trunk mode has captured that:
You can see that the 802.1Q tag has got captured. I am not sure whether you have noticed that the first three bits in the tag has been set to be 101 which is 5 in decimal. That is to illustrate that the QoS classification at level 2 can be done via setting the CoS bits which are carried by the 802.1Q tag.
Diagram:
You may find simpler way to do it in somewhere else’s blog (e.g. packetLife) but my idea comes the characteristic of broadcast. That is the broadcast will send out to everywhere in the broadcast domain including ports which are in TRUNK mode on the same switch. Configuration is simple as suggested in the diagram. And I just send a ping to 10.10.10.255 from PC1 which is in the same network or VLAN and the wireshark running on the PC2 which is connected to the trunk mode has captured that:
You can see that the 802.1Q tag has got captured. I am not sure whether you have noticed that the first three bits in the tag has been set to be 101 which is 5 in decimal. That is to illustrate that the QoS classification at level 2 can be done via setting the CoS bits which are carried by the 802.1Q tag.
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