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Automating bulk OPNsense Unbound DNS host overrides

03.25.2025 by William Lam // 2 Comments

I recently deployed OPNsense in my homelab, which I will be using it to setup my VMware Cloud Foundation (VCF) environment. A critical part infrastructure service that is often miss-configured is DNS and OPNsense provides a simple way add your custom DNS entries (forward/reverse) called Host Overrides, which uses Unbound DNS behind the scenes.

Like most, I have a number of DNS entries that I would like to pre-create and the UI is not exactly the quickest for any type of "bulk" operation as each entry is added sequentially.


Luckily, OPNsense does have a REST API for Unbound functions, but the documentation was not very useful as it just direct users to use the browser to extract the JSON payload, while something I am comfortable with, I think that is not what I expected from something called an API Reference ...

In any case, this was a simple enough API, that I was able to create a quick PowerShell script to parse a CSV file that contains the list of FQDN, IP Address and Description and then perform a bulk create since the API itself was also sequential in nature 🙁

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William is Distinguished Platform Engineering Architect in the VMware Cloud Foundation (VCF) Division at Broadcom. His primary focus is helping customers and partners build, run and operate a modern Private Cloud using the VMware Cloud Foundation (VCF) platform.

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