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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Nick Kelly

Cybersecurity Engineer, Cisco

Nick has over 20 years of experience in Security Operations and Security Sales. He is an avid student of cybersecurity and regularly engages with the Infosec community at events like BSides, RVASec, Derbycon and more. The son of an FBI forensics director, Nick holds a B.S. in Criminal Justice and is one of Cisco’s Fire Jumper Elite members. When he’s not working, he writes cyberpunk and punches aliens on his Playstation.


Virgilio “BONG” dela Cruz Jr.

CCDP, CCNA V, CCNP, Cisco IPS Express Security for AM/EE
Field Solutions Architect, Tech Data

Virgilio “Bong” has sixteen years of professional experience in IT industry from academe, technical and customer support, pre-sales, post sales, project management, training and enablement. He has worked in Cisco Technical Assistance Center (TAC) as a member of the WAN and LAN Switching team. Bong now works for Tech Data as the Field Solutions Architect with a focus on Cisco Security and holds a few Cisco certifications including Fire Jumper Elite.


John Cavanaugh

CCIE #1066, CCDE #20070002, CCAr
Chief Technology Officer, Practice Lead Security Services, NetCraftsmen

John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies. Previously he has held several positions including Executive Director/Chief Architect for Global Network Services at JPMorgan Chase. In that capacity, he led a team managing network architecture and services.  Prior to his role at JPMorgan Chase, John was a Distinguished Engineer at Cisco working across a number of verticals including Higher Education, Finance, Retail, Government, and Health Care.

He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes. John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.