F5 LTM deployment across 2 DC's.

Using only LTM leads to the following design questions:

What will happen if one data center internet link goes down, how are you going to redirect the traffic to the other data center? Do you have intelligent DNS services or are you simply going to add multiple A records to your external DNS server and do round robin without intelligent monitoring? The business has to address this risk by accepting it or dealing with it using GTM.

Are both datacenters connected at layer 2, in other words are vlans replicated between sites if so you could realize one cluster?