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Note: I think my question has a poor title but I am not sure how to fix it, so please correct if you think of something better.
In my office our phones are equipped with a "daisy-chain" port so that users may plug in both their phone and PC into a single network port.
One of our users messed up and connected the daisy-chain port back into the network (as there were two data ports). This created a ton of problems very quickly and it was only due to dumb luck that I discovered the misconfiguration.
Even while the phone was doubly-connected I was able to connect to other network machines and even browse the web, albeit extremely slowly. There was packet loss and high latency while pinging other machines on the network.
I am wondering:
- What was happening while the phone/switch was doubly-connected?
- How would you diagnose something like this without unplugging stuff from the main switch or patch panel?