Network Size and Automation

Terry Slattery
Principal Architect

I’ve observed other people running various size networks and have worked in a number of networks of various sizes myself and want to share my thoughts on when automation is needed to help manage a network.  I’ve personally done a manual network discovery of about 50 routers (in 1990), hired a consulting company to do a network audit of about 150 routers and switches (in 2000), and worked on a financial network rollout (in 2001).  I’ve also seen how excellent networking teams manage networks of more than 2000 routers and switches.  As a result my rule of thumb is that when a network grows to more than about 20 to 50 routers and switches, depending on the level of expertise of the network team, an automated system is required to help with the management.

Why is automation needed?  As the number of network devices grows, the time needed to keep an eye on all the facets of its operation grows.  Adding another 50 port switch increases the extent of VLANs and adds a group of new access ports that need to be properly configured and should be monitored to detect problems.  What would I check on switches?

  • Root bridge selection
  • Host setting on access ports (portfast, BPDU guard, loopguard, duplex settings)
  • Management IP address and ACL to restrict access to only network management systems
  • Detecting ports that have duplex mismatch (even though the switch config was correct)
  • Ports with high utilization (important for potentially oversubscribed uplinks) or high errors
  • VLAN definitions
  • Environmental exceptions (high temperature, failed power supplies, etc)

Adding another router to the network adds a collection of routing details to check regularly.

  • Routing protocol definition and authentication
  • Loopback address definition
  • Access Control Lists
  • Interface configurations
  • Interface errors, congestion, and utilization
  • CPU and memory utilization
  • Environmental exceptions (high temperature, failed power supplies, etc)

Imagine checking the above characteristics on a regular basis (even once a week) without a mechanism to automate the data collection.  Even if you have something that helps automate the collection, you’ll want something to help sort through the collected data to identify those items that need your attention.

The network staff at Ball State University understand that automated tools are needed, as explained in the article at:

Linda L Briggs, “Ball State Dials in Network Management,” Campus Technology, 12/13/2007,

Daniel Fortriede, Ball State’s senior enterprise/network engineer, describes their environment and describes how automation helps them manage their network.  The reasons are identical to the concepts I describe above.  Think about how good it would be to have a regular check on the configurations of all your network equipment, and whether the  way it was installed changes the intent of the configuration (see my other blog posting titled The Importance of Configuration and Operational Views of the Network).



Re-posted with Permission 

NetCraftsmen would like to acknowledge Infoblox for their permission to re-post this article which originally appeared in the Applied Infrastructure blog under


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