HowTo create a Site-to-Site connection with my side in Subnet?

[Elmar]

Hello there,

first off please forgive my bad English, and my lack of knowledge.

I want to create a Site-to-Site connection to one of our Customers. On our side the tunnel should end in a custom Subnet so that no traffic can reach my main Network.
Our current Network is 172.24.0.0 with a Netmask of 255.255.0.0

As i am new to pfsense and the whole IPsec VPN as well as to routing and firewalls in general i would really appreciate the help of some more experienced people like you.
My questions are:
How do i create a new Subnet on pfsense ?
How do i route the traffic of some of my Users traffic to the tunnel?

I already tried to find some comprehensive info on that Topic but really couldnt find any source that could explain some of those basic Tasks to me, so please have mercy with me.