@EnterpriseArchitect , there is no complete Azure alternative solution that can replace bastion. Having said that you can still be able to reduce the IP vulnerability attacks like Brute force attacks and DDoS attacks using the below solutions,
1.Deploying NSG on the subnet with necessary I/O security rules should block the IP access to certain IP's.
2.Deploying a VPN Gateway and connecting on microsoft backbone. In this method you can connect to VM using its private IP. This includes pricing.
3.Configuring Just-in-time access by configuring it through an Azure Virtual Machine blade or configure a JIT policy on a VM programmatically. This reduces the risk of attacks as the port will be closed until you access.
4.Deploying a jump host and hardening it with NSG. This increases infrastructure cost.
So, deploying the Azure Bastion is the best solution to provide a complete security solution.
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