Time savers and cool Cisco IOS tips

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Time savers and cool Cisco IOS tips

Like This Blog 0 Mark Jacob
Added by April 2, 2012

How about some cool tips designed to make your life easier maybe a little more fun at the same time? Today I want to share a couple of things you might find useful or downright mind blowing (if you’ve never seen it before).

If you use the Cisco IOS with any frequency, you have probably mistyped a command and then waited for what seemed like eons to get your console back. After this happens a couple of times, you likely typed this command from global configuration mode: no ip domain-lookup There, it’s fixed. Now if you mistype a command, you get your console back immediately. But what if you WANT domain name resolution? Have you ever tried this? Once again, from global configuration mode, type the command ip name-server X.X.X.X (where the X’s represent the IP address of a real DNS provider). If you have typed the “no ip domain-lookup” command, now you have to undo that by typing ip domain-lookup in global configuration mode. If you have not changed the default behavior, then ip domain-lookup is enabled. Once these steps are done, ping something by name, such as www.cisco.com. Your router will receive replies from this ‘name’ ping. Cool stuff! For further reading on this topic, see this Cisco article: Configuring DNS on Cisco Routers

While we are talking about name resolution, here’s another time-saver. Let’s say you are bouncing around between your network devices for testing or configuration purposes. If you are repeatedly hitting the same device by its IP address and are just plain tired of typing it, from global configuration mode, try this: ip host {name} X.X.X.X where the Xs are the IP address of the device you are repeatedly accessing. Here is a screen shot:

IP Host names Cisco IOS tips and time savers











I have just typed the command ip host Switch and hit the question mark to see my options, one of which is to enter the IP address as A.B.C.D. Once again, just this little step will save you headaches later. You can now ping this device by the name you configured, or you can telnet to it by its name as well. Give it a shot and see what you think!

If you are bouncing around you devices in your network, you’ll find very quickly how easy it is to forget which device you connected to from which. Many net admins are familiar with the show sessions command to see what’s live. A short version of this command, which is a pre-configured alias on many Cisco devices, is to just type w and hit Enter. This is an alias for the ‘where’ command. The results are the same as if you had typed show sessions. If you are curious, type show alias to see the ones that are already configured before you add any. Now that you have seen the power, let’s say you want to use it yourself. If you have never created an alias before, it is not difficult. Let’s say you want to create an alias for copy run start because you are tired of typing it over and over. Here is how: From global configuration mode, type alias exec crs copy run start. The crs part is whatever you want the short version of the command to be. The copy run start part is what the short version of the command represents. From now on, when you type crs, the device will treat that as if you had typed copy run start. Keep in mind that copy run start is not the full version of the command. The full command is copy running-config startup-config. So you see once you have decided on the shortcut version of your command, the rest can be the unambiguous version of the command you are shortening. Cool, right? The last piece of this is that you still must type the shortcut version in the correct context of the IOS for it to work. If you are in interface configuration mode, for example, and type copy run start, what happens? It fails, right? So typing crs in the same context will fail as well.

I hope you have some fun with these ideas. Happy configuring! Until next time…

Mark Jacob
Cisco Instructor – Interface Technical Training
Phoenix, AZ

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