DNS Express is a feature that has been around since the 11.1 days, and it's one of the more powerful features offered by the BIG-IP. DNS Express allows you to transfer DNS zones from your current infrastructure to the BIG-IP. The BIG-IP can then answer requests for those zones...and do it at blazingly fast speeds! Check out this week's edition of Lightboard Lessons where we discuss all the goodness of DNS Express.
It should also be mentioned that all too often when installations use Zone Runner DNS Express is omitted from the config. Please please please, never resolve from Zone Runner(on box BIND). Setup DNS Express to server your Zone Runner zones. I don't see this recommendation enough. DNS Express works with Zone Runner the same way it works with off box DNS servers. There's even a nice code share on DevCentral that will script creating your DNS Express zones using your Zone Runner named.conf config. https://devcentral.f5.com/codeshare/add-dns-express-zones-for-all-zones-in-namedconf
Also, don't forget to setup notify so when you make changes they are transferred into DNS Express.
https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/dns-services-implementations-11-...
