How to force network packets across network instead of loopback

Hello, I have two network interfaces ix0 and ix1 on the same FreeBSD
host. When transferring data between those interfaces, is there a way
to force FreeBSD to send and receive packets across the physical
network, instead of using loopback? I'd like to use this for NIC
hardware testing.

I tried adding various static routes, but this does not seem to work.

Thanks.