Publishing web site with 2 firewalls

[XBH]

Hi,

I'd appreciate input on the following:

I've got 2 WAN connections (different ISPs, multiple IPs each) and 2 pfSense boxes. DHCP on LAN is configured to send 2 default gateways to clients for the outgoing traffic failover/load balancing.

I'd like to have load balancing/failover for the incoming traffic as well. I've have set up port forwarding to the server I want to publish.

This setup will work with one IP only as the IIS box sends responses to only one of the boxes. To make it work I can add a second NIC and configure each of the NICs on the IIS box to use different pfSense box as default gateway.

I can do that on Windows machines (mostly VMs), but I also have couple of appliances where the manufacturer allows only single IP/NIC.

I've tried playing with NAT Reflection, but to no avail. Having read documentation bit deeper I understand it may not be for the purpose I'm trying to use it for.

Is there any other way to configure pfSense (and/or network routing table) other than the 2 NIC setup to achieve the above.

Regards,

Xbh

[XBH]

I understand reverse proxy could help, although I'm not sure the appliances in question would be happy with it.