Networking

Get a better grasp of Cisco commands with the Output Interpreter

Have you ever entered a Cisco command and been completely overwhelmed by its output? Some commands can return dozens of pages of output, and it's easy to feel like it's in a foreign language. David Davis tells you how Cisco's Output Interpreter acts as your translator in the language of command output.

Has the output from a Cisco IOS command ever completely confused you? Who hasn't been in this situation? How many times have you looked at some IOS statistics and weren't sure what the numbers meant? Help is only a click away.

The Cisco Output Interpreter is here to solve these types of problems. Registered Cisco users with a service contract linked to their account can access this free Web site, which will "translate" that cryptic output for you.

The Output Interpreter is a very cool tool. All you need to do is paste in some Cisco IOS output from a show command, and it works like a language translation Web site. You can upload the results from just about any Cisco IOS switch, router, or even PIX command, and the tool will tell you what's important — in plain English.

This tool has been around for some time, but Cisco continually improves it to offer results for more commands and to make the output more useful. The Output Interpreter can interpret the output from most show commands. You can even submit the output from several different show commands, and the tool will interpret all of them. Cisco offers a limited list of supported commands that this tool will interpret for you (login required).

Let's use the show command as an example for using the Output Interpreter. First, make sure you're submitting the entire output from the command, and make sure the command is on the list of supported commands.

Second, determine why you're submitting this command for analysis. To help you out, Cisco offers another tool called the Problem To Command Mapping Tool (login required). Using this tool, select the problem you're having, and the tool suggests show commands to run and submit for analysis.

Once you know why you want to use the Output Interpreter, you need to log into the Web site. As I mentioned before, to access this tool, you must be a registered Cisco user with a service contract linked to your account.

You can either paste the output from multiple Cisco IOS show commands in the blank space, or you can upload a text file that has the command output. For this example, I used the show running-configoutput from a small, partially functioning 871W router. Figure A shows a screenshot from the Web site.

Figure A

Paste the output in the supplied box.

Figure B shows a screenshot after I received the results.

Figure B

After you submit the output, the tool "translates" it for you.

Although my configuration was very basic, the interpreter provided a great deal of information — 10 pages if I had printed it. Here's some of the information the tool provided:

  • It lists errors, warnings, status, and helpful references.
  • For every recommended IP command, it provides a URL link to the command's explanation.
  • The tool performed a security and network address translation (NAT) analysis on my configuration.
  • The tool recommended beefing up security by enabling username/password login security and other security settings.
  • It also suggested using access control lists (ACLs) to prevent IP spoofing, control traffic flooding, enable logging, and more.
  • The tool offered recommendations for improving my basic NAT configuration.

For a second example, I used the show tech-support command on the core router on my network. The output was 75 pages if printed, so I turned to the Output Interpreter. Figure C offers a screenshot of the results.

Figure C

The Output Interpreter provides a great deal of information.

The 58-page output I received was pretty impressive. Even on a fully functioning core router, there were 30 errors, 147 warnings, 93 status information flags, and 19 helpful hints.

In my opinion, here are some of the best commands to submit to the Output Interpreter:

  • show running-config (router and PIX)
  • show tech-support
  • show interfaces
  • debug x (router and PIX)
  • show controller
  • show diag
  • show isdn x
  • show memory
  • show version (router and PIX)
  • show process cpu

This tool offers a ton of verbose information. However, if I am able to resolve even one serious issue with this analysis, it's worth the time. The Output Interpreter doesn't just point out the issues — it often tells you how to resolve them. That's the kind of tool we can all use.

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David Davis has worked in the IT industry for 12 years and holds several certifications, including CCIE, MCSE+I, CISSP, CCNA, CCDA, and CCNP. He currently manages a group of systems/network administrators for a privately owned retail company and performs networking/systems consulting on a part-time basis.

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