[ti_ranger]

> What people use in those sitations is Anycast.

This requires that you blow a publicly-advertisable prefix for every unique combination of services you would want to fail-over.

E.g., if you wanted to be able to have independent fail-over between your customer-facing self-service portal and your webmail interface (each relying on specific state that you can't replicate synchronously, and can't guarantee replicate consistently with each other), you would need to /24s, one dedicated to anycast for the webmail interface, one for the self-service portal, and separate from any services which are active-active.

Whereas using DNS, you could use your other existing public /24s that you are already using for your active-active services.

In the last days of IPv4, an extra 2 /24s just for this is quite an expense.