CCIE Pursuit Blog

January 24, 2009

Monkey See, Monkey Doo-Doo

Filed under: Cisco,Cisco Certification,IOS — cciepursuit @ 4:03 pm
Tags: , , , ,

The IE blog has a great post up about the ‘show parser dump’ command.  I was connected to a production 6500 at work while I was reading this, so I decided to follow along with the blog post and run the commands on the switch.  They’re just ‘show’ commands so there shouldn’t be any problems right?

I had entered ‘show parser dump interface | include ^15_(.*)ospf’ and looked through the first screen of output.  I hit the spacebar to get the next page……and nothing happened.  I hit the spacebar a couple more times and still nothing happened.  The switch was locked up.  Nooooooooo!!!!!  Suddenly sick to my stomach I waited helplessly, hoping that the switch would return.  It finally did many (loooooooong) seconds later.

WS-C6509#sh hist
  show parser dump route-map | include ^15_
  show parser dump interface | include ^15_(.*)ospf

WS-C6509#sh proc cpu hist
100           ******************************************
 90           ******************************************
 80           ******************************************
 70           ******************************************
 60      ****************************************************
 50      ****************************************************
 40      ****************************************************
 30      ****************************************************
 20      ****************************************************
 10      ****************************************************
             0    5    0    5    0    5    0    5    0    5
               CPU% per second (last 60 seconds)

The CPU was pegged for about 45 seconds.  If I had read the whole post I would have seen that these commands can be ‘CPUHogs’ but I had not read ahead.

Lesson learned!  Don’t experiment on production gear.  Save it for the lab…and save your job.  🙂



  1. It’s actually not the parser dump that is the CPU hog, but the regexp that I used. In production you’d be better off saying “terminal length 0”, log to a file, then just “show parser dump interface”. Afterwords just sort through the textfile to find the commands you need.

    Also I should probably start all my posts with a disclaimer now. 😉

    Comment by Brian McGahan — January 24, 2009 @ 4:48 pm | Reply

    • @Brian McGahan – Good to know. “Disclaimer: Internetwork Expert will not be responsible for boneheads who test features on production equipment.” 🙂

      Comment by cciepursuit — January 25, 2009 @ 4:43 pm | Reply

  2. There is an unspoken mantra among network analysts and engineers alike, “Real men test in production networks!”

    So I guess, welcome to manhood. 😀

    Comment by Aragoen Celtdra — January 25, 2009 @ 11:08 am | Reply

    • @Aragoen Celtdra – My ‘manhood’ crawled up into my chest when the switch locked up. 🙂

      Comment by cciepursuit — January 25, 2009 @ 4:44 pm | Reply

  3. Been there, done that…We’ve all done it ! Real men do test on production gear—Smart men learn not to make the same mistake again…but since we are real men, we continue to test other “features” in production !!!!!!!!!

    Comment by kevhat — January 25, 2009 @ 4:30 pm | Reply

    • @kevhat – LOL. You’re right. I won’t try that particular command on production gear again….but that won’t stop me from eventually doing something similar.

      Comment by cciepursuit — January 25, 2009 @ 4:45 pm | Reply

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