Good Network Design

Terry Slattery
Principal Architect

Good network design follows long-established principles like hierarchical design and information hiding. Basic network protocols exhibit this through data encapsulation. Lower layers hide their operation from the upper layers, allowing changes in the lower layers to not impact the upper layers (i.e. applications).

Network design recommendations are to use a Core, Distribution, and Access layer design. A concept that’s overlooked in this type of design is that one goal of the distribution layer is to prevent changes in the access layer (where end stations connect to the network) from affecting the core. The core should be designed to operate at maximum packet forwarding efficiency so as to provide high reliability, low latency, low delay, and low packet loss. In a sense, the distribution layer operates much like OSPF areas do – summarize changes in the access layer and only present to the core the summary information. Said another way, the distribution layer insulates the core from changes that occur at the access layer, allowing the core to be more stable and efficient.

I had not seen this idea specifically presented until a few weeks ago at a Cisco University presentation in Columbia, MD, and I thought it was worth sharing with a wider audience.



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.