ON THE WIRE

Strange But True Tales From The Net Crypt

by Bill Alderson and J. Scott Haugdahl

In our July 1 column, we noted a problem involving a 3745 front-end processor attached to a token ring. Whenever it was attached, massive ring errors occurred. Despite the frantic efforts vendors made trying different token-ring adapters and cables, the solution was to implement a simple gender change with a media filter. This month we'll share with you even more bizarre- but-true stories that we've encountered in our day-to-day troubleshooting experiences.

Bill: Hey, Scott, what say we start with the one about the service guy on a cold, winter day?

Scott: I thought we were only going to discuss hot problems.

Bill: So, there's this service person who had been trying to solve a customer's intermittent Ethernet problem.

Scott: From time to time, the network would take a hit, and several users would lose their connections with the file server.

Bill: One day, the service person came to the customer's site, removed his jacket, draped it over the top of a cubicle on top of a pile of other jackets (yes, this was the coat rack), and coincidentally, a person in a nearby cubicle immediately complained that the network went down...

Scott: żand a light bulb went off in the service person's head. You see, in cold climate areas, it gets very dry in the winter. As it turned out, throwing a jacket over the cubicle generated static electricity that would bring the network down more often than not.

Bill: The solution was simple: Ground the cubicles, but not through the Ethernet cabling!

Scott: Our next problem was very illuminating.

Bill: Ah, yes, the ol' flashlight tale.

Scott: A client had a file server that consistently crashed early in the morning--around 5 a.m. They couldn't find anything wrong with the power, file server or anything else that would cause such a problem.

Bill: Left with no alternative, they decided to camp out overnight in the office.

Scott: After trying to stay awake all night, they were in a groggy state when they were startled awake by a loud bang. Now alert, they saw an eerie beam of steady light shining from one end of a long hallway.

Bill: Looking at their watches, they realized it was close to 5 a.m. and they knew they were on to something.

Scott: Peering down the hallway, they saw the night watchman making his rounds. After the initial surprise of their sudden and rude awakening, the troubleshooters decided to check out the light source.

Bill: So that he wouldn't have to carry his flashlight, the night watchman would routinely slap a powerful magnetic flashlight against the metal case of the file server to illuminate the hallway when making his rounds.

Scott: Although we didn't know which was worse, the slap or the magnet, the solution was simple: Carry the flashlight! And perhaps relocate the file server to a more secure location.

Bill: Good thing they solved the problem the first night.

Scott: Why is that?

Bill: They were already getting low on hot dogs and marshmallows.

Scott: And now, a few 10BASE-T wiring stories.

Bill: When we troubleshoot networks, we sometimes need access to wiring closets.

Scott: We always like to be pr epared for a big problem when going onsite, so we like to examine the network documentation and check out a couple of wiring closets first.

Bill: Some wiring designs are methodically planned and installed, from the desktop to the last twist at the hub port connector. With careful labeling and good documentation, we can quickly relate problems we analyze to ports where devices are plugged in.

Scott: So during our first day onsite at a particular client, we asked to check out a wiring closet.

Bill: We were led down a rather long corridor with cubicles on one side and a solid wall on the other.

Scott: Finally we stopped walking and our client said, "Look up."

Bill: So we did, and lo and behold, there was the "wiring closet."

Scott: Now we've seen neat and we've seen ugly, and this one was definitely the latter.

Bill: There was this hub, with hundreds of 10BASE-T Category 3 wires coming out from a hole in the ceiling to a hub mounted at the intersection of the wall and the ceiling.

Scott: If we hadn't spotted those 49-cent "L" brackets from the hardware store holding up a piece of scrap wood upon which the hub rested, we would have sworn that the hub was held up by the cables coming from the ceiling.

Bill: It was amazing that the system worked at all, but work it did and very well at that. Thankfully though, we didn't have to pull out the extension ladder to troubleshoot a problem.

Scott: That reminds me of another 10BASE-T problem that had no end.

Bill: While troubleshooting a problem, we happened to be in a wiring closet (down to earth this time) and noticed the collision light frantically flashing on a nearby Ethernet hub.

Scott: Tracing down the ports, one particular port's LED was indicating a high rate of errors and collisions.

Bill: When the cable was rem oved, the high collision rate ceased. With aid from our client, we tracked down the connection to a particular workstation.

Scott: The wiring was one continuous length of Category 5 wiring from the hub all the way to the wall plate near the workstation.

Bill: When we got to the other end, we noticed that the drop cable from the wall plate to the workstation wasn't even connected to the workstation's adapter.

Scott: So, naturally we suspected a cabling problem. A more interesting observation was why the hub even activated the port in the first place, given that there was no active connection at the other end.

Bill: Since there was no patch panel between the hub and workstation, the only wiring components that needed testing were the hub-to-station cable run, faceplate and station drop cable.

Scott: Every component checked out and when isolating the hub-to-station cable run, it passed the Category 5 cable test from both ends.

Bill: Ultimately, it turned out to be a hub problem.

Scott: It was definitely the first time we'd seen a hub link enable light come on by plugging in a good cable with absolutely nothing attached to the other end!

Bill & Scott: If you've got a favorite horror story to share, send it to us at otw@pmg.com. We'll pick our favorites and publish them in a future column. Those whose stories we publish will receive an exclusive "Tales From the Net Crypt" T-Shirt!ż

Bill and Scott are the principals of Pine Mountain Group. They can be reached at otw@pmg.com. Portions of actual trace files from selected columns are available via Pine Mountain Group's Home Page (http://www.pmg.com).

November 15, 1995