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

[irishmasms.livejournal.com]

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.

x-posted to tech_moment & techsupport

Comments

[jecook]

::BANG!!::

Ow. My head explodiated.

SSC: I have done that to avoid either moving a wall drop, or running a cable all the way around an office, but with our offices, the users are generally unaware of the network stuff.

I'm surprised that the little desktop switch didnt ioslate the ports in question. I have an old, old 3com 10mbit hub that will do that if someone tries to pull that type of stunt.

[torkell]

Heard of it happen.

IT admin at my previous school was fiddling with stuff in the core comms cabinet. He spotted a free end of some red Cat5. Now, red Cat5 is used there for backbone links. So, assuming it must have been accidently unplugged, he plugged it in to a free switch port and wandered off.

Later that day the network was very congested, so he wandered down to the comms cupboard to see what was up. I don't think I need to spell out the rest.

[lions-tambua.livejournal.com]

ARGL! :)
spanning-tree wont work so good with non-manageable switches causing an loop ;)
but the idea is great *G* i could try that here, lets see how long our IT takes to find the problem *muahahaha*
-------
ok, joke aside, quote: "Some people are still alife, only because its illegal to kill them"

[ihateemo.livejournal.com]

Hahaha, that's a great story.

[brotherflounder]

*wipes Diet Coke off monitor*

Oh dear...