IPSec vpn disconnections due ISP problem

Hi, i have IPSec vpn configuration with 2 WAN connections used by the VPN for redundancy.
What it happens if the first ISP - WAN connection has problem but the VPN connection is still up?
How the second one ISP knows about the problem and how it takes the role as master WAN ISP?

What else i need to configured on PepLink 580 under WAN Connection Priority?

Device Information
Model: Peplink Balance 580
Firmware: 6.3.1 build 3471

Thanks,

The WAN connection priority setting is all that is needed. If the primary WAN connection has a problem the Balance will fail its health check. In that case the VPN will re-establish out to the secondary ISP.

Yes, but what about if the primary WAN connection (ISP provider) has international connectivity problem (with their PoP connections example London PoP) and my IPSec VPN is still up with the specific ISP?
How the Balance knows about the problem? And in that case how the balance will re-establish out the VPN with the secondary ISP?

Thanks,
Andreas.

This is a limitation of IPSec itself compared to our proprietary SpeedFusion VPN. You would have to manually switch the IPSec tunnel to use the other WAN.