Bandwidth, VLANs, and 10 G Links

Peter Welcher
Architect, Operations Technical Advisor

In the middle of a deployment, Jim Marinelli and I discovered a small surprise (to us, anyway). Recent SXH or SXI code, possibly VSS in the mix. (I’d like to have narrowed it down further for you, but there’s been no time to do testing of various variations.)

Jim saw that OSPF wasn’t using the direct 20 G etherchannel crosslink between two switches. The switches are ASBR’s between two OSPF domains, so we ran two VLANs across the crosslink, to allow OSPF adjacencies within each OSPF domain (We do the same thing with ABR’s: have one link or VLAN on each “side of the border” to prevent potential odd routing paths, especially under failure conditions.)

Upon investigation, the bandwidth for the VLAN SVI interfaces was 1 Gbps, where we’d have expected them to inherit 20 Gbps. 

Setting the bandwidth manually resolved the problem. 

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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.