Peplink_VPN_Multiwan

Hi Guys,
I Have 1 peplink 305 model, has 2 WAN line: 1 main and 1 back up.
i had configed IP Sec VPN IKEv2 with another Cisco device- with the main line
I consider when the main line have problem(down, faill…) the IPSec VPN traffic will to through back up line or not?
If i config multiwan for IPsec VPN on Peplink, how it work? do you have any document about this?

tks so much