Show 22 – Configuration Management – Whys, Wherefores and War Stories

This week, Terry Slattery from Netcraftsmen ( and Josh O’Brien talk network configuration management and experiences. Ethan is taking a break from the microphone.

Terry Slattery was the first or the second CCIE depending on how you look at it, and the founder of Netcordia, a network management product for Automated Network Change and Configuration Management tool. We are looking at his Top 5 common network configuration errors, the problems and they cause and what you can do about them with Network Management tools. Terry currently works at Chesapeake Netcraftsmen performing network management consulting and network assessments for a variety of clients.

Terry’s Top 5 network problems.

  • Layer 1 – Duplex mismatch.
  • Overlarge VLANs and STP domains, increasing potential for forwarding loops – more common than you would think.
  • root bridge not defined or unstable root bridge
  • many routers with static default routes defined (and in general, heavy use of static routes is not good. Terry’s advice – use the dynamic protocols to distribute default. Inject statics at the border where connections exist to partners
  • lack of route summarization (related to a good IP addressing plan) Terry points out that route summarisation increases routing stability by limiting address range to a geography. Try to limit the number of summarized ranges.
  • first hop redundancy protocol with only one router defined which is redundancy failure waiting to happen
  • poor configuration change control processes – discussion ranging from configs not matching corporate policies to lack of a change control system and config archive

Terry’s Perl script for summarising Syslog entires to get useful data.


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Greg Ferro
Greg Ferro is a Network Engineer/Architect, mostly focussed on Data Centre, Security Infrastructure, and recently Virtualization. He has over 20 years in IT, in wide range of employers working as a freelance consultant including Finance, Service Providers and Online Companies. He is CCIE#6920 and has a few ideas about the world, but not enough to really count. He is a host on the Packet Pushers Podcast, blogger at and on Twitter @etherealmind and Google Plus.
Greg Ferro
Greg Ferro
Greg Ferro
Greg Ferro

Latest posts by Greg Ferro (see all)

  • Jeremy Arnold

    Hi Greg,

    Loving the Podcast.. More on this type of podcast, with common network issues easily solved.

    I also need to ask one favour?? I think its the ADD in me thats asking this..

    can you agree on a naming convention?? I can't sort out on my phone, nor in iTunes as you have different naming conventions. i.e. Show 21 or Show-22 ?? also the band, and album are all different.

    I know i'm being anally retentive, but its really difficult to sort and my phone finds it difficult to sort.

    Keep up the great work!!

  • killabee

    Great podcast today guys, love it! Keep it up.

  • Carl Von Hassel

    Great show. Love the podcast. However I do have one comment, I disagree about the statement concerning auto duplex and speed settings and how well auto negotiation works. I have seen numerous times where Tandberg endpoints and Cisco 2960 series switches simply will not negotiate correctly. Trust me when I say I would much rather have negotiation work then manually adjust the settings. Needless to say an incorrect duplex/speed setting on a device that performs video conferencing is problematic. I also seen numerous problems with Cisco switches and HP workstations.

    • Greg Ferro

      How many videoconference units do you have out of the total number of ethernet ports ?

    • Dur

      Try using cat 6….

  • Carl Von Hassel

    I have around 60 Tandberg Codecs mostly Edge 95 but also some 3000 MXP and 990 MXP. I also run into the problem on HP PCs running Tandberg's Movi client. Switchports number around 10,000 where switches are typically Cisco 2960's. Tandberg Codecs support 10/100, Cisco 2960's 10/100 and some 10/100/1000. Auto negotiation works about 25% of the time. Just getting the port up is a task, it takes various combinations to get the port on line. Either 100/full on the Codec and auto/auto on the switch or auto/auto on the Codec and 100/full on the switch. Sometimes 100/full on the Codec and 100/full on the switch works. Cabling is all Cat 5E. It is annoying as hell and I hope now that Tandberg is owned by Cisco that the problem will be rectified.

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