In this chapter, I’ll give you a checklist of performance and health items that may come in handy when you’re blindsided with a vague complaint about the network being slow. Even if the complaint comes from just one user, you’d be remiss not to tentatively investigate. This checklist will give you some clues as to whether you need to eliminate the network as a problem or investigate further. I emphasize that this checklist is not a troubleshooting guide. It’s only going to tell you if there’s a problem—not necessarily what that problem is or how to fix it.
In addition to providing a checklist, I’ll show you how to check each item. Some of this you’ve seen before, and some of it will be new. Keep in mind that you may have to work through this checklist on multiple devices in your network. It’s rare that a network problem will manifest itself in an obvious way on every router and switch. By the way, all the IOS commands I show you in this chapter, with one exception, will work on both routers and switches. I’ll point out that exception when we get to it.
Here’s the checklist: