I love it when old tried and true methodologies still ring true.
A great example is my old favorite; VLAN, broadcast or subnet analysis. This is one of my favorites for various reasons;
I don’t need a span or mirror port
I get to see how various network devices are configured such as STP, OSPF, CDP, etc
Same as number 2 but for the client
In this video, I show you how to use Wireshark and filter on DHCP, then spefici client conversations as well as see the effects of some old ip helper or dhcp relay configs that pointed to the local dhcp server.