techrecovery | From a friend - a funny MDI/MDI-X autodetection story (Reply)

From a friend - a funny MDI/MDI-X autodetection story

An enterprise customer of mine, who shall remain nameless, has a number of locations and 336 managed switch ports, primarily Cisco Catalyst 2924 and 2950 series switches.

Their facilities are older, they're growing quickly, and there are a few places where they choose to install those small Linksys or Netgear
desktop switches. A steady diet of unmanaged devices in a network that size will give you an ulcer, but a few dozen ports done that way is no big deal ... or so we thought.

We don't like DHCP problems so we've set spanning-tree portfast on all the Cisco boxes except for the few places where we've got L2 redundancy in the network. Instead of fifty seconds of spanning tree the stations get instant service so their DHCP requests don't time out on them.

One of the smaller locations has a show floor and a small common area where executives will sit with their laptops when they're on site. It was served by a small desktop switch. One day a nameless executive from the nameless enterprise finished his work and, wanting to keep things tidy, coiled up his network cable, plugged the free end into the autodetecting desktop switch port, and walked away for the day.

Four hours later after much driving on my part, much grumbling from the staff at the location, replacement of their switch, replacement of
their router, and much other horsing around, we finally isolated the source of the 142% CPU utilization on the switch.

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