GTM Failover over two internet connection from two DCs

Hi All,

 

i have little doubt regarding GTM.

 

We all know about tracking the Primary WAN interface from WAN router and to switch to Secondary WAN router on WAN link through hsrp.

 

Now, I would like how GTM will failover to secondary internet connection?

 

Objects Are : Distributed Application under both GTMs, Two DC (DC1 and DC2), EIDE IP, listener IP ,

 

both GTMs monitoring DC1_link & DC2_Link , Server and virtual server etc.

 

Does GTM tracking internet/wan connection through some mean for failover ? Or the DC_Link is the failover decision taking object?