GTM Topology Question/Problem

I'm trying to configure what I believe to be fairly simple -

A WIP that uses topology load balancing to send users coming from 172.26.100.0/24 to one VS, and users coming from 172.26.101.0/24 to another VS.

We delegate individual hostnames to the GTM like so in our DNS:

hostname IN NS gtm1

Each end-client uses DNS servers in those respective networks (ie, 172.26.100.10 and 172.26.101.10). If we query the GTM's directly from 172.26.100.0/24, we get directed to the correct VS per the topology rule. If we query the GTM's directly from 172.26.101.0/24, we also get directed to the correct VS.

However, if we query "hostname" through our normal DNS servers which delegate 'hostname' to the GTMs (172.26.[100,101].10), we don't get the expected response. We seem to be getting a response based on the origin/address of the DNS server, not the client's IP address.

Shouldn't the GTM reply to a query based on the client request, and not the DNS server which delegates to the GTM?

Josh