DNS record question for Link Controller

quite new to F5 LC, so my question is

after deployment of F5 LC, the dns server should have 2 ns records and 2 a records for 2 isp. when client from internet do a dns request, the dns server will reply either record by round robin.

 

lets say customer site to isp1 link down, but dont think the dns server will know about this, may i say still got 50% chance the dns server will reply the dns request with the isp1 record which is already down.

 

 

 

will this happen? really thanks :)