GTM DNS flapping issue

Currently set for Preferred=Round Robin/ Alt=Round Robin/Return to DNS

Change your preferred to "global availability". Round-robin will rotate between all pool members that are passing health checks. Global availability will return the pool member with the highest (closest to 0) order that is passing health checks. If no pool members are available for GA, then the LB method will try using the alternate method, and finally will fall to the fallback method.

Awesome. and thanks Saggy. I will for sure try this

Just one last question I had on this since i haven't received a maint window to test settings. Why is it that I have several other VIPs setup with Preferred=Round Robin/ Alt=Round Robin/Return to DNS and they never flap between pri/sec DNS entries?

It's difficult to say without seeing it. First thoughts are: secondary VIP(s) is/are failing health checks in the GTM pool, the DNS name is not actually delegated to the GTM listeners and some other DNS service is answering, or there is a different LB method at the wideip-level that sends requests to a different pool. there could be other possibilities, but I'm not privy to your GTM/LTM configuration norms or DNS setup. I do know, though, that by definition, round-robin will round-robin through live VIPs in a GTM pool. Are you testing functionality using nslookup?

yes last week i was testing using my external DNS server when i saw the flapping so I deleted the secondary VIp DNS .Weird thing is today I re-added the DNS with no changes to pool or Wide Ip and it now works