A topic that I blocked about, VLANs in the DMZ was taken up both by Ivan Pepelnjak and Colin McNamara . Colin points out that security is more about what is done in the complete path and not at a single point. There are a few extra points I would mention: Data should not be stored in a DMZ terminating incoming external connections. These should be limited to processing. It is a theoretical physical exploit and not a remote one. There has been no major security incident attributed to VLAN hopping as a cause. After all these years, with cloud and virtualization up to our eyeballs, I wonder if Ivan will admit I was right?
This is the blog of Ronald Bartels that wanders on and off the subject of problem management (that is how it started). Mostly now the topics are about IoT and SD-WAN.