[HOWTO] OpnSense under virtualisation (Proxmox et.al.)

[meyergru]

You must be very careful with dual-homed hosts:

a. they should not route packets between interfaces
b. that includes setting the gateway on the correct interface

Normally, you use this only in order to be able to reach the machine via a second "leg". I do that sometimes, when I have a VM that lies behind a reverse proxy with a "LAN" leg and I still have a direct IPv6 connection. In such cases, the LAN side has no gateway at all, because the reverse proxy accesses it via its own LAN IP.