I am wondering if anyone has clever thoughts on how to address the situation with Topology load-balancing on F5 DNS. If a user is in EMEA but their ISP DNS server is in the US, it will be that DNS server in the US whose IP is analyzed by the geolocation database on the F5 and the GTM will respond with the DNS entry appropriate for US IP addresses. This circumvents our geolocation intent. Is there anything anyone has come up with to do to address this?
This is exactly why EDNS Client Subnet was created. Of course that depends on the ISP DNS server including the client subnet information and on your BIG-IP DNS running a version that supports the option.
Beyond that, not much to offer. This is a real and recognised weakness of global load balancing.