The Copier Man Rings Twice …and Then Some–A Tale of a Spanning Tree Loop (a Sequel Every Millisecond)

Have you ever wondered …what would happen if?  …if say …say

…if say you decide to plug that unknown loose wire into say …some open port on that switch that is conveniently close by? …well let’s just pretend even if you wouldn’t – I mean you are a mere copier printer tech guy …why should you be sloppy and leave loose wires sitting around unplugged? …you remembered unplugging it from the business machine you worked on moments ago and so you know it shouldn’t be loose …its like extra bolts when working on your engine – they gotta go somewhere – that machine is a network aware device and logic might dictate that a network cable should plug into the port on the side that magically happens to have a matching shape to that thing at the end of the loose cable …but that switch has lots of other wires in it – that looks like a better place …right?  I mean it does look inviting. [DOH!]

…so if you take a mini-switch that expands your limited one port wall plate in the corner to use a couple of printers, an IP phone, scanner …etc. you have a time-bomb waiting to detonate your network with ARP traffic.  Perhaps labeling the switch exactly as it is to be used would help to idiot proof it …or maybe taping over the unused ports.  The above fun was done at the expense of a real scenario but the names were changed to protect the guilty.   Unplugging all hosts from the main relay rack switches and adding them back one at a time was the methodology that first brought relief and ultimately led to the conclusion that a spanning tree loop condition existed somewhere out in the office.  The pain of seeing a network go berserk and not know why was unsettling for many hours of down-time until the client remembered that a copier/printer guy had done work the previous day.   It was a matter of minutes then to get things rectified.

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