That network consultant from Chicago was wrong about VLANs

Guy named Mark came in to audit our setup at the office park. Told me to ditch all VLAN segregation for a flat network. Said it'd simplify things. Two weeks later we had a broadcast storm that took down the entire building for 4 hours. Had to rebuild the VLAN config from scratch. Has anyone else had an "expert" give advice that just wrecked performance?

2 comments

2 Comments

spencer_ross28d ago

Whoa hold on there. I'm not gonna defend that Mark guy because flat networks are a disaster waiting to happen, but saying VLANs stop broadcast storms isn't really accurate either. Broadcast storms usually come from loops in the network, like someone plugging in a switch wrong or a bad NIC going haywire. VLANs can actually make things worse if you have a storm in one VLAN because it can still take down that entire segment. And if your switch is cheap or configured badly, the storm can leak into other VLANs too through the trunk ports. So yeah, that consultant was dead wrong about ditching VLANs for security and traffic control, but blaming him for the storm itself might be missing the real problem. You probably had a loop somewhere that the VLANs were accidentally masking before.

carr.willow27d ago

After that consultant cleared out our VLANs things went sideways fast, so I feel your pain. We ended up keeping the VLANs for security but ran a cable tester across every wall port and closet to find a bad patch cable that was causing our own loop issues. Fixed both problems at once and never looked back.