• Azure Firewall documentation
• Azure Firewall Manager policy overview
  • Rule Processing on Azure firewall.

Rule Processing Summary:

• Outbound - First match wins
  • Network rules in order of priority (low to high)
  • Application rules in order of priority (low to high)
• Inbound - First match wins
  • DNAT rules in order of priority (low to high)
  • Match also allows the traffic.

• Microsoft Azure ‘Route Based’ VPN to Cisco ASA

The above is the article that got it working for me. It was my first route-based VPN and I was missing the crucial info about the weird interface addressing. It's only used for routing and otherwise not needed.