I find out issue is about name resolving, because addresses are rightly routed.
How can Forticlient resolve fqdn according to 2 dns (internal DNS over vpn, external DNS which is my home router). How Can Forticlient distinguish a dns request? That is if It must be routed to internal dns or to external dns?
DNS servers are checked from top to bottom which means that all your DNS queries will go to the DNS server which is defined under SSL VPN configuration. If the first DNS server is unable to resolve, the request goes to the next DNS server.
Apologies, I didn't put it into correct words. You are right, the second DNS server will be queried only if first DNS server is unreachable.
I don't understand... the first DNS, which is the DNS of VPN, resolves ONLY ip addresses of LAN fqdn. If I make query about external name, e.g www.google.it, my 1st DNS will not able to resolve it, and query will not be forwarded to 2nd dns (because 1st is reachable)
2nd DNS is the home router which is able to resolve external domain.