Using LTM as secondary caching DNS server with GTM-DNS license
We have a small remote data center with a few dozen servers and a BigIP pair running version 11.6.0.
The servers need to use internal DNS in order to function, and are configured to use our internal DNS servers at our main data center. This works great 99.9% of the time, but once in a while the site-to-site VPN connecting the two data centers will become unreliable and DNS queries will time out. The hostnames frequently change IP addesses, so using hosts entries isn't a viable option.
I noticed the BigIPs had a 'GTM-DNS' license, so it seems I could use them as secondary or caching DNS servers. This would be a great option, because I can assume the LTMs will always be available. I was able to add the nameservers and zones, but now the question is how do I get the servers to actually use it? With a full GTM license I would create a listener, but that's not an option with the GTM-DNS license.