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  • Router Buffer Tuning

    Buffer tuning has long been an interesting topic for me. I recently found a blog post by Brough Turner, who wrote an interesting article about a potential misconfiguration of AT&T wireless routers that cause ping round trip times to be either <...
  • Cisco Fan Failure

    Have you ever had a Cisco router or switch shutdown due to a fan failure? While looking through NetMRI's daily list of analysis issues, I found a Fan Failure issue (it is named "Device Fan Problem" in NetMRI's Analysis page). It was...
  • Cisco Router Interface Wedged

    We recently had an interface wedge on a customer router, with some interesting repercussions. The network topology is shown below. Every day from about 8am until 6pm, a 250Mbps - 300Mbps traffic load starts between the Major Facility and the core network...
  • What is Bridge Assurance?

    While doing some other research recently, I ran across the Bridge Assurance feature in Cisco gear, which was new to me. Cisco has been working on ways to avoid STP melt-down and Bridge Assurance is another tool to help network administrators keep networks...
  • Spanning Tree Protocol and Failure Domains

    Co-worker Pete Welcher recently helped a customer whose network experienced a spanning tree loop (i.e. a melt-down). Several things can be learned from thinking about the experience and how to avoid it. Lesson #1: Adequately plan the task. Rush jobs carry...
  • Identifying Unsaved Running Configurations

    Have you ever lost a device configuration because you forgot to save it to NVRAM and the device later rebooted, perhaps due to a power outage? More than likely some feature or function that had been operating correctly since the last change suddenly stopped...
  • Interview with TrainSignal posted

    I just finished an interview with Matt Elias at TrainSignal Training and they posted it at http://www.trainsignaltraining.com/first-ccie-terry-slattery/2009-12-08/ . Matt asked a bunch of questions around training and certification. Of particular interest...
  • Auto-negotiate Duplex or not?

    I've done a number of network assessments in which I find that the customer insists on manually configuring the interfaces for full duplex. I did a little research on the topic and found an interesting paper by Jim Eggers and Steve Hodnett at Sun...
  • Saved by the Configuration Repository!

    We recently had a near-disaster occur at a customer. A 6500 10/100 ethernet blade had died and was replaced. When the replacement blade was installed, the configuration for its interfaces disappeared from the configuration! The techs couldn't figure...
  • Network Availability and High Availability Networks

    Scott Hogg of Global Technology Resources (GTRI) did a nice blog post for Network World way back in April, 2009 about High Expectations of Network Availability (http://www.networkworld.com/community/node/40827) and a slightly more recent one in May, "...
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