Analyzing VLANs and VLAN tagging issues

VLAN, or Virtual LAN, is a mechanism that divides a LAN into separate LANs without any connectivity between them, and this is where the name virtual comes from. In this section we will have a look at recipes to monitor VLAN traffic.

The purpose of this recipe is to give the reader a general description of how to use Wireshark for VLAN issues. An easier way to solve related problems is to use the vendor's CLI (Cisco IOS, Juniper JUNOS, and so on) for this purpose.

Getting ready

We will discuss two issues in this recipe:

  • How to monitor traffic inside a VLAN
  • How to view tagged frames going through a VLAN-tagged port

In the first case, a simple configuration is required. In the second case, there are some points ...

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