This is a follow-up to the OVH + Failover IP address setup, with articles this time! I had used ESXi in the last article, but felt like using the Proxmox virtualization this time around. I found that pFsense WAN could connect to the internet, but my virtual machines could not. I found that some weird default route wasn't created. This was probably due to the weird failover IP that OVH/SoYouStart gives you.
Anyhow, create a simple shell script and run it at boot time. Place it in the directory below; example shell script below.
route delete default route add -net [MAIN IP].254 -iface [pFsense WAN] route add default [MAIN IP].254 /usr/local/etc/rc.d/
Additionally, I had to use an internal bridge with the WAN and NOT create a new interface with the IPs. Looks like it is an "OVS Bridge." This bridge was then used to create the LAN network.