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Azure offers services like Azure Express route and Azure VPN which you can use to connect your on-prem private networks to the virtual networks on Azure. You can go through this article which provides recommended connectivity approaches for using Azure PaaS services
Azure Express Route: You can use Azure ExpressRoute to create private connections between Azure datacenters and infrastructure on premises or in a colocation environment. ExpressRoute connections don't route through the public internet, and they offer more reliability, faster speed, and lower latency than typical internet connections.
To access the PaaS services mentioned above in the question you can use Private endpoints integration for them to bring into your virtual network and then use Azure private peering of express route to establish connectivity. You can refer to this sample architecture for additional details.
Azure VPN : Azure VPN Gateway is a service that uses a specific type of virtual network gateway to send encrypted traffic between an Azure virtual network and on-premises locations over the public Internet. Azure VPN is suitable for hybrid applications where the traffic between on-premises hardware and the cloud is likely to be light, or you're willing to trade slightly extended latency for the flexibility and processing power of the cloud. You can refer to this sample architecture for additional details.
Hope this helps! Please let me know if you have any additional questions. Thank you!
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