High-Level Network Design and Etherchannel Load Balancing

Terry Slattery
Principal Architect

After the experience with a wedged router interface (see prior post: Cisco Router Interface Wedged), several of us at Netcraftsmen were discussing etherchannel load balancing and what to recommend to customers and how to check the setting in network equipment.

James Ventre made a very good point for using src-dst-ip as the load balancing algorithm.  Each pair of src-dst IP addresses will be sent on one of the etherchannels.  His argument is that using IP addresses makes the load balancing operate much like equal cost multipath routing, even though it is a switching algorithm, not a routing algorithm.

Using src-dst-ip allows you to continue to think about configuration and troubleshooting at Layer 3 instead of having to switch between Layer 3 and Layer 2 as you examine and think about the packet flows through the network.

Take James’ idea and apply it throughout the network design.  Where possible, make sure that you are consistent in how your design works and favor design choices that simplify or make packet flows consistent.  What I realized is that by making this simple change in how I look at network designs, I can more easily make choices about alternative configurations.  Using this high-level thought process, one of the configurations will have clear advantages over the others.  It is something that can be documented in network policy documents, which get used in network design, network operations, network troubleshooting, and network management.  That’s a big impact.

Thanks, James, for helping elevate my design thought process.



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 http://www.infoblox.com/en/communities/blogs.html


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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.