iApp f5.dns Question

I think that iApp sets up a pair of virtual servers - one for UDP and another for TCP - that both load balance DNS queries to a pool comprised of the servers that you entered. With such a setup, BIG-IP shouldn't be doing anything to the replies other than passing them back to the client. Things to look at that come to mind:

 

 

1. Are the servers in the DNS pool being marked up by their monitors? If the servers are down, is it because of a networking issue like the BIG-IP not having a route to reach those servers, or is the LTM just not happy with the data in the reply?

 

2. What does tcpdump on the BIG-IP show for the traffic that is sent from the BIG-IP to one of the DNS servers? Is the server responding back with a correct reply?