DEMO: Getting Help in Cisco IOS

The Cisco IOS has a lot of commands, and it can be confusing what parameters a certain command needs, or what mode has certain commands available to it. That's why Cisco IOS has a built-in feature that can provide some help for you.

The question mark is context specific

So what I'm going to do is get onto the switch right here, and it's going to start out in the user exec mode. I'm going to issue it the question mark, so I'm going to hit question mark, and what it's displaying here is a list of commands for this mode. So for the user exec mode, this is the list of commands that's available to it.

I can actually get into the privileged exec mode, so I'm going to get into the privileged exec mode and do the same thing, and we'll notice that this list of commands is different. So it's context specific: whatever mode that you're in, that's going to be what commands it shows you for that.

Scrolling through the output

Another thing I'll note too is it's scrolling through this display. Anytime your Cisco equipment can't display enough information on one screen, then it might pop up with this more. It's going to list out some of the parameters and then it's going to be more, and then to scroll through this I can hit enter and scroll line by line. So the enter key will allow you to go line by line through these, or I can hit the space bar and it's going to go page by page through these.

Let me do that one more time, and I'm in the middle of this. Let's say, oh, really what I was looking for is I wanted to know the clock command, and now I can see that clock is in here, that's what I want to use. So I'm done scrolling through. I can hit tab to scroll through the rest of it, or I can just hit any key and then that stops scrolling through there.

Narrowing the list of commands

All right, so back to the question mark. First of all, what we've discovered is the question mark will show us all of the commands for a certain mode. Or, if we want to sort it, if we know that the command that we want to use starts with an s, we can do s question mark and it's going to show us all of the commands that start with s. Or maybe we know that it starts with s, e, so we hit se question mark and it's going to show us all the commands that start with se.

Let me do that one more time here, s, e. So I can see now that send, set and setup are the three options that it gives me.

Finding the options for a command

In this example, let me do show. I know what I want to do is view into something, and I can do that with the show command, so it's probably a show command that I want. So which show command do I want? I do show space and then question mark, and now what it's showing me is the sub commands for this, or what options I have with the show command. So now I see this big long list, and I find the one I want. Maybe the one that I really wanted was interfaces. So that's what I want.

I'm going to get out of here by hitting any key. I'm going to do show interfaces, and now what options do I have for show interfaces? Once again there's a fairly lengthy list with this. In this particular case I want to point out that there is a CR, or carriage return: this is your enter key. So really what it does is, it's fine on its own. I can do show interfaces right now. In fact I'm going to hit enter, and now it's showing me all of the interfaces, and it's showing me an extensive list of data for those interfaces.

When the command isn't recognised

So next, I don't want to see every one. The switch has a lot of interfaces, so I want to pick out a specific interface. So what I'm going to do is get out of this, so hit any key to get out of this. I'm going to do show interfaces, and then let's say, oh, I think it's a fiber connection, maybe I type in fiber connection, so maybe that's what I want. I'm going to hit enter.

So another thing besides just the question mark that can help you out: it's going to specify here that show interfaces fiber is not a command, it doesn't recognize it, and it actually gives us another piece of information here, invalid input detected at the caret symbol marker. So whenever you see the caret symbol there, that's going to show you where it's struggling with it. It understands everything up until that caret, so it understands all of that, but then says, I lost you right here, so what are you trying to say? So it doesn't recognize that.

I'm going to go back and delete that first part, and maybe do the question mark to see what other options I have: filter, groups. No, that's not what I wanted. So now that little caret helps us determine where we went wrong with this.

Narrowing down to one interface

All right, now I want show interfaces. What I'm actually looking for maybe is a fast ethernet interface, so I'm going to type in fast ethernet, and what parameters do I need for this? So I'm going to hit question mark, and now what it's looking for, for fast ethernet, is the specific interface number. So now I need to type in an interface number. So for this one, fast ethernet, maybe I'm looking at 0 14. I want to know what the status of 0 14 is. Hit enter, and I can see now this interface is up. I can see some stats along the lines with this interface, and scroll through, and I don't have to look at everything because I've narrowed it down to a specific interface.

Really what you need to get out of this is that the help is with the question mark. So you type things in, and it will let you know which commands you can use for the different modes, and you can hone in on what parameters you need for those commands. So the question mark can be very helpful as you're trying to navigate through the Cisco IOS.