Normally I talk about overlays in the context of data center/SDN/cloud but today I'm going out into left field and am going to talk about voice! :-)

I freely admit that I'm a noob when it comes to Cisco voice so I'm not sure if the behavior I'm about to describe is obvious or not. It wasn't obvious to me and I only figured it out after running into the issue for real and troubleshooting it to resolution.

The issue stems from my misunderstanding about how dual-line ephone-dns function when used in an overlay.

I've been working on something that at this point in my career I never thought I'd be doing: another Cisco Certified Network Associate (CCNA) certification. The CCNA Voice, to be exact. Now that I'm in a job role where I'm expected to be somewhat of a jack-of-all-trades, I can no longer avoid learning voice :-) For a long time I've focused on just the underlying network bits and left the voice "stuff" to others. Since I now need to talk intelligently about Cisco voice solutions, products, and architectures, I decided to go through the CCNA Voice curriculum as a way to establish some foundational knowledge.

This post is about the tools and methods I used to build a small lab to support my studies.