Hi,
For your Azure setup with a public IP for Azure Firewall in a Hub VNet and backend applications in a Spoke VNet, you should apply Azure DDoS Protection Standard to both the public IP and the virtual network. This protection will cover the public IP attached to your Azure Firewall and extend enhanced DDoS mitigation capabilities to your entire virtual network, including your backend applications. This approach ensures comprehensive protection against DDoS attacks for both the network entry point and the internal network infrastructure.
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