Phones, printers and cameras drop on every floor at once

At 09:40 phones, printers and cameras across all four floors go offline together. PCs in VLAN 10 still work, and you can still SSH to every switch over the management VLAN 99. The only change today: a technician connected SWLAB, a switch borrowed from the lab, to a spare wall port on ASW3 to give a test bench network access. The campus runs VTP version 2 with DSW1 as server and the access switches as clients.