DPD is Preemptive?

HI All,

i have a question about DPD. As i know, DPD is used to monitor the reachability of VPN Peers, right? Ok, i have one vpn tunel established with Peer A, and the client will include a new internet connection in the same vpn gateway. They ask to us to include a secondary Peer in the vpn configuration. But now, i would like to know if Peer A turn down, the Peer B will be considered and the vpn should be established with Peer B, normaly. Ok this is expected. But, and about the Peer A back to UP? Will automatically, the vpn be established with the Peer A again? DPD is preemptive?

Sorry, for my english.

Thanks,

João Victor