Nimbostratushi
We have 2 big ip 2200 - active-standby with 2 internet service provider 1 primary Dns server and 1 dns secondary server that we intend to forward the requests to the big-ip resolver responding to the client with the ip address of the available service provider. Not informing the ip address of the service provider down. In that case do we have to configure DNS Express or Zonerunner on bigIP? What is the best option?
EmployeeBigIP DNS is not really intended to be an end user resolver. It's intent is to serve resolvers. Zone Runner is a front end for the BIND server running on the BigIP, while DNS Express is intended to be a high speed secondary name server.
In fact you can configure both. You could have Zone runner pull from your primary DNS Server, and DNS Express pull from your local BIND.
You can read more about Zone Runner here: https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-dns-services-implementations-13-0-0/14.html
and DNS Express here: https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/bigip-dns-services-implementations-13-0-0/1.html