How to configure the use of the interface only for forwarding on the VM-router?

Question

linux

I have a network diagram shown in the picture:

Explanation:

1. "Server1" has 2 network interfaces "NIC1" and "NIC2".
   
2. On Server1, "VM1" is raised from virtualbox, on which pfSense is installed (software router\proxy\firewall)
   
3. "VM1" is configured with 2 network interfaces of the bridge type for each of the physical NICs of Server1.
   
4. NIC1 receives a cable from a provider with an external IP
   
5. NIC2 is used as a LAN interface and receives settings from pfSense on VM1, where DNS/DHCP is up.
   

What is required : I need NIC1 on Server1 to be used ONLY for passing traffic to VM1, so that in the end I can learn the standard WAN <---> firewall<---> LAN scheme, where Server1 is the LAN node of the network.
Otherwise, I get 2 nodes looking outward (Server1 and VM1).
How to implement it?

Answer 1

Remove the IP address from the physical nic1. Let the default gateway for server1 be the IP address of pfsense's internal virtual interface