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Show-22-Configuration Management — Whys, Wherefores and War Stories

This week, Terry Slattery 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’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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About the author

Greg Ferro

Greg Ferro is the co-host of Packet Pushers. After surviving 25 years in Enterprise IT with only minor damage, he uses his networking expertise for good in the service of others by deep diving on technology and industry. His unique role as an inspirational cynicist brings a sense of fun, practicality and sheer talent to world of data networking and its place in a world of clouds.

He blogs regularly at and the podcasts are at

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