This came about from deciding to switch from Route53 to Cloudflare for DNS management. I’d already prepared the destination zones on Cloudflare but needed to update the mechanism I had in place that manages the DNS entry for the dynamic IP address. The mechanism was a NodeRED flow that made an API call directly to Route53. I’d need to do some research on how to do the same on Cloudflare.

Given what I now understood from working with ’external-dns’, I figured I could save some time by somehow leveraging it’s ability to manage DNS entries in multiple third-party DNS providers as changes are made to Ingresses and Services in the cluster it is deployed to.

I did a quick check to see whether using an IP address in an ‘ExternalName’ service would work, and sure enough it worked as expected.

kubectl create service externalname dynamicip1 --external-name `curl icanhazip.com`
kubectl annotate service dynamicip1 "external-dns.alpha.kubernetes.io/hostname=office1.dynamicip.golder.org"

After a while, it checks out…

kubectl get service
NAME         TYPE           CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE
dynamicip1   ExternalName   <none>       125.26.38.8   <none>    99m

So I came up with a bit of Golang imaginatively called update-dynamic-ip, which I now run in a container on a QNAP NAS in the office.

It should be pretty straightforward to understand how to build, configure and run it, but time is running short toda so I’ll add a README to the repo another day that will cover all that.

UPDATE: README now added.