A listener is a specialized virtual server that uses port 53 and to which you assign a specific IP address. When traffic is sent to that IP address, the listener alerts BIG-IP GTM and the system either handles the traffic locally or forwards the traffic to the appropriate resource.
You control how BIG-IP GTM responds to network traffic on a per-listener basis. The number of listeners you create depends on your network configuration and the destinations to which you want to send specific DNS requests. For example, a single BIG-IP GTM can be the primary authoritative server for one domain, while forwarding other DNS requests to a different DNS server. Regardless of how many listeners you configure, BIG-IP GTM always manages and responds to requests for the wide IPs that you have configured on the system.
Perform these tasks to replace a DNS server with BIG-IP GTM.