What will be with MySQL cluster if network problems between nodes?
It will be decided by an arbitrator node which is normally a MGM node.
It would be advisable to put this arbitrator node in a 3rd DC.

In the case of 2 DCs the DC where the arbitrator resides will survive
if the network between the DCs is broken. With a 3rd DC with the arbitrator
node, the one to first ask for arbitration will fail.