Application and Service Dependencies

Terry Slattery
Principal Architect

I regularly exchange information with the folks at Chesapeake Netcraftsmen (, who often encounter interesting real-world troubleshooting scenarios.  This time it was Rick Burts, who happens to be the top Cisco NetPro participant (see background info on Rick below).  He described the following scenario:

“The customer contacted me Thursday to say that during the day a problem developed on their VPN concentrator (3000 series). It was no longer accepting any VPN sessions. I was able to establish a management session to the concentrator. In doing some troubleshooting I determined that the problem was that the concentrator was no longer able to communicate with  its authentication server. It turns out that their network admin had shut down that server in the morning – not realizing that it was a crucial part of their VPN environment.”

When I read this, I recognized the problem as a regular occurrence.  Someone on the staff doesn’t know the set of dependencies between devices that implement a service or application.  That’s why dependency mapping is so important.  If there had been a dependency map available, the network administrator could have easily checked to see what services and applications depended on that server and taken a different approach that would have avoided the outage.

Similar scenarios occur when critical communications gear is taken down.  A similar result would have happened if the switch providing network connectivity to the authentication server was taken out of service for maintenance.  Dependency mapping isn’t just about the clients and servers; it is also about the infrastructure supporting the communications between other devices.  This is what network analysis is about.


* Rick is the top of NetPro participants is at Top NetPros
Other links: Rick’s NetPro Bio; The Cisco NetPro Forum


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


Leave a Reply


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.