Configuration Rollback

Terry Slattery
Principal Architect

We were talking with Debra Curtis of Gartner yesterday about Network Configuration and Change Management (NCCM) and the topic of Rollback came up.  Juniper has supported the ‘commit’ operation since they started, allowing their devices to be rolled back easily.  However, Cisco only recently added the ‘commit’ feature and when you examine it carefully, you find that it doesn’t always work the way you want (e.g., rollback of ACLs is problematic).

A basic rollback function re-installs the old configuration and expects the device to use that configuraiton instead of the old one.  What most managers expect is that the rollback will restore the device to its prior state without a service interruption.  That’s not what Cisco IOS does – the configurations merge (to some degree) when a second configuration is loaded into a running box.  To get back to the original configuration, you have to load the configuration and then force a reload of the box, resulting in a service interruption.  Yuck.

Loading the inverse (by adding or removing the word ‘no’ on the begining of the command) of the most recent configuration commands will not necessarily restore the desired configuraiton state either.  Double-yuck.

In yesterday’s blog post, I mentioned a Network World blog by Jamey  Heary in which he describes new features of IOS 12.4(20)T.  In it is a description of the Auto-upgrade manager, which includes non-stop upgrades whereby a whole new IOS is loaded and started while the forwarding plane continues to run.  Jamey called it a warm start.  It’s a good feature.

What if the warm start feature were used in the reload operaton to implement a full rollback (the whole configuration is loaded into the device)?  The forwarding plane can continue to run while the current image reloads the configuration, re-establishes neighbor relationships, then updates the forwarding plane as needed.  I’ll bet that someone at Cisco has already thought of this, or maybe it is documented elsewhere and I’m not aware of it.  If not, please add my name to the patent application. Wink



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.