I recently ran into an interesting issue with my home Kubernetes environment that runs my blog. As I mentioned in a previous post, I run my blog on k3s and I use cert-manager to manage my SSL certificates provided by Let’s Encrypt. Let’s say that I’ve temporarily changed my Internet provider and along with it, my router. This router does not appear to support NAT Loopback. The cert-manager documentation acknowledges the issue but doesn’t provide much of a solution. Cert-manager couldn’t renew my blog’s certificate because its self-check kept failing. I managed to solve the issue through a fairly simple CoreDNS change. Let’s take a look.
One of my favorite questions to ask (or be asked) during an interview is the classic “how does the Internet work?” question. It usually goes something like this:
You open your favorite web browser, type in “www.mysite.com”, and hit return. Almost like magic, a fully-rendered web page shows up on your screen ready for you to view. Tell me, with as much detail as you can muster, what just happened.
The reason I like this question so much is that it isn’t just academic; it is a peek behind the curtains at what this person knows. It reveals what they’ve dug into in the past, learned in school, or dealt with while troubleshooting. The details show how much time they’ve spent demystifying the world (at least related to our working environment). Thinking about this made me realize how really fleshing out a solid answer to this would make a great blog post, so here we are.