Just to be clear, are you lord balancing DNS using LTM module, or using DNS module for GSLB and DNS screening or hosting? I will give some guidance for both scenarios:
- LTM: Just keep the respective VS or pool members disabled. Manually bring them up.
- GTM: Easiest way is upstream DNS records. Delegate to only Production GTM listener, and if you need to failover, the. modify this configuration to delegate to DR instead. Although, think you mention the DR F5 doesn't have the GTM/DNS module provisioned?
Finally, remember GTM uses a component of LTM under the hood. If you want to delegate to BOTH, but just receive responses from Production, then just manually down the LTM VIP used as the GTM/DNS listener. You can always enable it during DR recovery procedure.