Subsystem Configuration Policy Check

Terry Slattery
Principal Architect

I’m working on a network that requires configuration checks be performed.  For some of the subsystems, that’s pretty easy because the configuration is done per device and there are no external dependencies.  For example, the desired SNMP, logging, VTY, or NTP configurations are well known and only vary when the configuration syntax is varies across device types or OS release. However, other parts of the configuration are highy dependent on data regarding how the device is installed and connected.  How would you handle identifying the differences in the capabilities of the various flavors of the WS-X6148 (48 port) switch blade in a 6500/7600 platform and apply the correct configuration to those ports?

My prime example for configuration dependency is the set of configurations that may be applied to switch ports.  If a port is used as an access port, it would have one configuration.  If it is a switch-to-switch link, it will have a different configuration.  And if it is a routed interface, it will have yet another configuration.  I’m not aware of tools that can take into account how a port is used and then use that to determine which of several configuration segments to use.

The same mechanism is needed for performing configuration updates.  When you’re trying to install a set of configuration updates to thousands of switch ports on hundreds or thousands of devices, doing manual updates is out of the question (unless you enjoy tracking down a lot of human error induced problems).  In this case, I may be modifying a QoS command across all my access ports.  I don’t want to rely on ports being reserved for specific roles because some switches will have a different number of ports than others.  Aggregation switches may have more down-stream switches than others, potentially altering which ports need to have QoS parameters changed or perhaps changing what commands would be used.

If you’re aware of any tools that can handle configuration checking and updates like those that I describe above, please let me know.



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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