I have a client that have Exchange 2010 with 2000 users that's split on two different geographical sites that are connected through MPLS and replicating changes simultaneously. Each exchange site has 4 servers (1 DAG with 2 mailboxes and (2 for CAS and HT).
The client had an IT company that applied the Exchange 2010 project for them thinking they have had redundancy but recently the site 1 had an internet problem (Cable was cut due to construction) and all the users on site1 stopped receiving mails....
That made me wonder how could one solve such a problem and how would Exchange on site 2 detect a timeout for mailboxes in Site1 ... notice that DAG on site 1 doesn't have users on site 2 and vice versa.
Would creating one DAG For all exchange servers handle the problem in case Internet was out in one of the sites? I would appreciate that.
I don't have more information now in regard to the infrastructure .