A quick way to drop all your telephones

Changing your switches from Spanning Tree Protocol (STP) to Rapid Spanning Tree Protocol (RSTP) is a Good Thing. Convergence in case of dropped redundant links goes from 50 seconds to 6 seconds.

Here is what I programmed on  my core/distribution switch, a Cisco 3750:

# en
# conf t
# spanning-tree vlan 1-4094 root primary
# spanning-tree mode rapid-pvst
(Complete and utter silence from the switch.
Angry noises from two cubicles over.)

Cold sweat. Fear.

Friends, make the change during a scheduled maintenance period, no matter the pressure. The change will take out the network for about 10s; not enough to disturb users surfing for data, but more than enough time to disconnect VoIP phone calls.