A storage account must remain reachable through its public endpoint for an on-premises integration server, but only one Azure subnet should be allowed to access it from Azure. The team does not want private endpoints or DNS changes. What should the administrator configure?
A service endpoint lets traffic from the chosen Azure subnet reach the storage account over the Microsoft backbone while still using the account's public endpoint. Adding the subnet to the storage account firewall rules then restricts Azure access to only that subnet. This meets the requirement to keep public access available for the on-premises integration server while tightly limiting Azure-based access without private endpoints or DNS changes.
Why this answer
A service endpoint extends the virtual network identity to the storage account, allowing you to restrict access to a specific subnet while keeping the public endpoint enabled for on-premises access. This meets the requirement of allowing only one Azure subnet to access the storage account from Azure without using private endpoints or DNS changes.
Exam trap
The trap here is that candidates often confuse service endpoints with private endpoints, assuming that service endpoints require disabling public access or that private endpoints are the only way to restrict subnet access, when in fact service endpoints allow selective subnet access while keeping the public endpoint active.
Why the other options are wrong
A private endpoint disables public endpoint access, but the question requires the storage account to remain reachable through its public endpoint for the on-premises server.
A SAS token restricts access to specific resources or operations, not network-level access. It cannot enforce that traffic originates from a specific subnet; the SAS token can be used from any IP address that has the token.
Assigning Storage Blob Data Reader to the subnet grants read access to blob data but does not control network access; the storage account's public endpoint would still be accessible from any IP, violating the requirement to restrict access to only one Azure subnet.
When would these options actually be correct?
When the requirement is to completely remove public internet access and only allow private connectivity from a specific Azure subnet, without needing public endpoint access for on-premises resources.
When the requirement is to grant time-limited, delegated access to a specific storage resource (e.g., a blob or container) without changing network rules, and the client can securely manage the token. For example, allowing a third-party application to upload files for 1 hour.
This option would be correct if the question required granting read-only permissions to blob data for resources in a specific subnet, without needing to restrict network access (e.g., when the storage account already has a service endpoint or private endpoint configured).
Why candidates pick the wrong answer
Candidates may think private endpoint is the only way to restrict access to a specific subnet, overlooking that service endpoints can achieve subnet-level restriction while keeping the public endpoint enabled.
Candidates may think SAS tokens can restrict access by source IP or subnet because SAS can include an allowed IP range, but that range is for the client's public IP, not an Azure subnet, and it does not replace network-level subnet restrictions.
Candidates may confuse role-based access control (RBAC) with network-level access restrictions, thinking that assigning a role to a subnet can limit network connectivity, when in fact RBAC only controls data plane permissions.