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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