A listener is a specialized virtual server that passively checks for DNS packets on port 53 and the IP address you assign to the listener. When a DNS query is sent to the IP address of the listener, BIG-IP GTM either handles the request locally or forwards the request to the appropriate resource.
Perform these tasks to replace a DNS server with BIG-IP GTM.
When you want to improve the speed of responses to DNS queries you can configure a BIND server to allow zone transfers only to the DNS Express engine on the BIG-IP system. You do this by adding an allow-transfer statement to named.conf on the BIND server.