IPv6 Addressing for Troubleshooting

Terry Slattery
Principal Architect

Pv6 and the addresses are big and difficult to remember.  Upon initial configuration of network gear, it is tempting to use the EUI-64 encoding (article with a definition of EUI-64 by Wendell Odom) and let the device create the interface identifier portion of the 128-bit address.  But how would that affect your ability to perform network troubleshooting?  Let’s say that you need to do a traceroute6 or ping6 across the network and DNS isn’t working.  You’ll need the target IPv6 address, including the interface ID (the lower 64-bits of the IPv6 address).

My recommendation is to assign the interface ID so that it is one that you know and is relatively easy to type.  I did some traceroute6 experiements and found that several sites have used this approach, showing interface IDs of ::1.  One site seemed to use their own locally administered address which was four digits.  You could encode other characteristics of the remote device using the digits provided, but I’m not sure that’s necessarily desirable.

What would be useful to encode into the host ID field might be the device type.  ::1 through ::f could be routers while ::11 through ::1f could be switches.  To reach the primary device of each type on a network segment, use the lowest number for that device type.  The secondary device of that type would have the next larger number (e.g. ::2 for a router).

If you encounter a network where EUI-64 addresses were used, a short-hand of ::0 is supposed to address the router(s) on the segment, but I’ve not seen it work in our test network.  Let me know if you’ve found it to work and how reliable you’ve found it to be.

How do you assign IPv6 interface IDs?



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

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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.