Cisco show commands provide real-time visibility into switch and router behavior, covering interfaces, running configurations, MAC address tables, ARP entries, and more. This content walks through the most commonly used show commands executed from privileged exec mode.
Show Commands Overview
The show commands allow us to have insight into this device and what this device is doing. This is not going to be an extensive list of the show command, it's just going to be some of the highlights, some of the show commands that you'll use often.
I'm getting onto the switch, so I'm going to hit enter to get onto it. I want to get into the privileged exec mode, so I am now in the privileged exec mode, which is going to give us a lot more options for these show commands. I'm going to type in show and then the question mark to see what options I have with the show command, and as you can see there is a lot available to us on which route we want to view into, what we want to take a look at. So I can see a pretty extensive list with this.
One example of the ones that you'll be using quite a bit is show interfaces. We look into here and we're going to see all of the interfaces and some stats available for those interfaces. So it's showing me the stats for these interfaces, and if I scroll through here it's going to scroll through all these stats and all this data for each one of those interfaces. So, quite a bit of information.
Perhaps I don't want to know all of the information about all of these interfaces because it's just too much, and maybe there's a specific one. To narrow down what we're looking for, I'm going to do a show interfaces and then type in the interface that I'm looking for. In this case I'm going to look for FastEthernet 0/14. Now I'm seeing the status for this particular interface is up, so it's plugged into a device, and I can see some of the broadcast that's happening and the bytes that are going through there. So I see some information on what is going through that interface, some stats and some statuses on that interface. That's how I can narrow this down.
Another one that you will be using a lot is show ip interface brief. Show ip interface brief shows us all of the interfaces on this device and gives us the status of those, and it shows it in table form, so that way we can very quickly identify interfaces that are up and maybe interfaces that are struggling, or just what interfaces are on this device.
So I can see that there are 48 of these FastEthernet ports, there's a VLAN, and there's a GigabitEthernet as well. I can see all the status of this, so that will definitely be one that you'll use.
Another one that you use a lot is the show running-config. Show running-config shows us the configuration of what the device is operating off of currently. As I scroll through here I can see the different settings that it's operating on. Remember, this could be different from what's on the startup-config. This running-config will just show us what is currently running, the configurations currently running on this device. I see a lot of interfaces in here, and if I had descriptions or something programmed on these interfaces I'd be able to see all of that. This is a pretty blank switch, so I don't see too much from that standpoint.
Let's say I want to drill down further. I want to see the running config, but I want to see it of a specific interface. This is a little shortcut that can help you really quickly narrow down to see what programming is on the interface. You just type in the show running-config interface and then you type in the interface that you want to address. I'm going to do FastEthernet 0/14, so I'll hit enter here, and then I can see what configuration is on this interface, which is pretty basic, it doesn't really have much. But that's a quick way of doing that.
If I want to know, does this match up with what is in the startup config, I can do a show startup-config and see what's in the startup config, and scroll through here. I can see that at this point I haven't saved anything, so really the two match up and they're the same configurations in both of those. The show startup-config is going to be one that you may use now and then as well.
Another one that you will probably use throughout here is, if you're dealing with some of the files, you may want to take a look at the flash. So you do a show flash and you can see the files that are inside flash.
Another one that I find is interesting is the show mac address-table. You hit enter and you can see the MAC addresses that are within this device and the ports that they are associated with. In this case right here, we really just see that we have only one real device that's connected to this, so it's connected on Fa0/14. It recognizes that MAC address, and then the rest of these are actually the device and they're all associated with a VLAN. We'll take more of a look at that MAC address table in the future. Just know that that's a command that can be helpful.
Another one that we can also take a look at is the show arp. Students often will get confused between the ARP table and the MAC address table, so I hope at this point in time you understand the difference between the two. But the show arp, there's nothing in this one because I'm not remotely connected to it, and so this device is not actively communicating out from the device to any specific piece of equipment, although traffic can flow through this switch.
There are some show commands. There's a lot more show commands that are available out there, but just know that you're going to be using a lot of the show commands, and the ones that I mentioned here you're probably using a lot more than some of the other show commands. So get familiar with those show commands, because it can really help you drill down into issues and correct things.
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