Dual WAN SG-7100 and UniFi Talk Install

[pokrifchakd]

I currently have 2 ISPs connected to my Netgate, which is configured for load balancing and failover. I have purchased a /29 block from ISP1, with one of the addresses assigned to my UDM SE sitting behind the Netgate. On the UDM SE, I’ve got a Talk instance up and running. The problem I’m facing arises when I failover to ISP2. Because I have my UDM SE addressed in the /29 (only using 1 WAN interface), there is no advertised route from ISP2’s network back to my UDM SE’s public IP address. I’ve implemented NAT on my Netgate, which has allowed the majority of traffic to successfully traverse the link. What fails is my whole UniFi Talk setup.

I’ve been playing around with NAT and port forwarding rules, and have been able to get outbound calls to establish, but inbound calls continue to fail. Does anyone know what is needed for inbound calls to work? Current rules attached for review.

SIP related FW rules:

NAT related FW rules:

[pokrifchakd]

Adding a network diagram, which I hope helps better describe the problem.