Using nginx sub_filter on IP ranges

While scrolling through the visitor’s report of my blog, I noticed visitors from a “strange” ISP: “Magistrat der Stadt Wien, Magistratsabteilung 01”, which is the IT department of the magistrate of the City of Vienna. Digging further through the logs, I found out they are a regular visitor, and so are multiple ministries, the Austrian unemployment service, and multiple other public bodies (Maybe more, but due to IP anonymization I only know about the ones that have their own subnets). So I’ve decided to give them a special greeting when visiting.

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