Which CLI config sets the preshared key 'Test' for all remote peers in a GRE over IPsec DMVPN?

The correct command is crypto isakmp key Test address 0.0.0.0 0.0.0.0 because it correctly specifies the shared key for IKE (Internet Key Exchange), which is responsible for establishing the IPsec Security Association. In DMVPN, the hub uses a single pre-shared key for all spokes, and address 0.0.0.0 0.0.0.0 acts as a wildcard, applying the key to any remote peer. The authentication pre-share and set pre-share commands are not valid Cisco IOS commands for configuring IKE pre-shared keys. crypto ipsec key is also incorrect as IPsec itself doesn't directly use a "key" command in this context; IKE handles the key exchange.