Loopback interface

[Gozer]

Hello,

I am looking to migrate to Opnsense from a Fortinet firewall.

Problem, on Fortinet we have a notion of loopback interface that we use for several things:
- in iBGP, to mount sessions directly from loopback to loopback
- in NAT, to use the /32 IP  of each loopback for conditional NATs
- in VPN, to mount tunnels directly on this loopback IP, and not on the WAN interface (especially when setting up the dual wan)

Is there one, or different, ways to respond to these problems ?

I have seen many posts on Virtual IP, but the documentation is not very clear about this feature and the fact that we can use these VIP for NAT or VPN (in any case, it seems to me impossible for the BGP).

The simpliest way to do that would be to create a Loopback ou Dummy interface, and to be able to use it as a physical interface, but I find no way to do that (except a ip addr add 192.168.40.1/32 dev lo, but it does not seem persistant)

Thank you for your answers,