Six Whys - Or, Never Trust Your Network Switch

by Jeff Atwood

on January 25, 2010

Remember Joel Spolsky's fine article "Five Whys"? Sure you do! It contained this paragraph:

Michael spent some time doing a post-mortem, and discovered that the problem was a simple configuration problem on the switch. **There are several possible speeds that a switch can use to communicate (10, 100, or 1000 megabits/second). You can either set the speed manually, or you can let the switch automatically negotiate the highest speed that both sides can work with.** The switch that failed had been set to autonegotiate. This usually works, but not always, and on the morning of January 10th, it didn't.

Guess what we woke up this morning (well, you don't really "wake up" at 3 AM, unless you're a vampire, but you know what I mean) to find?

My, that looks familiar. Where have I read about this before? Oh yes, the article I just quoted twenty seconds ago!

To be fair to NetGear, we never had any port speed negotiation problems with our old 8-port GS108T switches, but we recently upgraded to the 24-port GS724T. I guess this model is more sensitive and brooding, or something.

Geoff "the Malice from Corvallis" Dalgas was all over this one and got all the web tier servers in our network set to a fixed, non-negotiable ethernet speed of 1 Gigabit.

And I ask myself ... why? why? why? why? why?

It's because I can't read, apparently, and that's why.