Big IP DNS Failover

Your BIG-IP DNS devices are synchronized but not clustered, unlike an Active-Standby setup in LTM. Instead, they operate in an Active-Active scenario, which is why you observe traffic on both devices.

This is an example:

1. A client makes a DNS query, which reaches your internal DNS.
2. The internal DNS responds with a CNAME pointing to a subdomain hosted on BIG-IP.
3. The client then queries the authoritative DNS for this subdomain and receives two NS records—one for each BIG-IP DNS.
4. The client selects one of these NS records randomly.
5. If the chosen NS does not respond, the client automatically retries with the second NS.

So, since both BIG-IP DNS devices function independently and actively, you can safely take one offline without impacting DNS resolution. The remaining device will continue handling queries seamlessly.