Is there a best practice IP address that is safe to use as a placeholder in a live public system on the Internet?
e.g. In a similar capacity, the domain name example.com is reserved and can be safely used without risk of this becoming someone's actual domain.
The context is that we have a custom Cloudflare firewall rule which allows access to a web-based system by matching a user's IP address. The user is able to remotely update the IP on the corresponding firewall rule to authorise themselves from another of our systems. We facilitate this update via Cloudflare's API.
Initially, the firewall rule requires a starting IP address which could potentially be in place forever, as we don't know if and when the user will use the system and update their IP. We also want to be able to revoke access after a certain time, by running a server task that resets all the firewall rules to the placeholder IP address again each night.
What should I do here? My first thought was to use a private IP address like
192.168.0.0 but this page made me question this.
Use caution when setting filters to exclude these private address ranges. In some cases, Regional Internet Registries (RIRs) have issued adjacent address space to their customers and that space is in use on the global Internet.
In August 2012, ARIN began allocating “172” address space to internet service, wireless, and content providers