Hi, 

I am trying to create a IPsec Failover for VPN tunnel (site to site) but the option for IKEv1 is disable in ER7206

IKEv1 is available only when the vpn policy is applied to a single Remote Subnet and a single Local Network.

https://www.tp-link.com/us/support/faq/3575/ this is what i tried to follow.