BIG-IP Global Traffic Manager (GTM) can function as a traffic screener in front of a pool of DNS servers. In this situation, BIG-IP GTM checks incoming DNS queries and if the query is for a wide IP, resolves the query. Otherwise, BIG-IP GTM forwards the DNS query to one of the servers in a pool of DNS servers, and that server handles the query.
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 screen non-wide IP traffic and forward the traffic to a pool of DNS servers.