We have one internet facing FW which is having 1 external Interface with some Public IP address range. While forming VPN between my organization FW and client FW. we are using virtual IP of external Interface of Firewall as peer IP for my organization.
Can we create sub-interface on external interface of Internet facing Firewall and assign one more public IP subnet and form VPN with Clients by using both physical and sub-interface external interface? Is this solution feasible?