Azure Private Endpoints: Keeping Traffic Off the Public Internet

Most Azure services default to public. That is not a criticism, it makes them easy to get started with, but "public by default" is a posture you should be choosing intentionally, not inheriting accidentally.

Private Endpoints are one of the cleaner tools Azure gives you to correct that. When you deploy a Key Vault, a Storage Account, or an Azure SQL database, it comes with a public address by default. Traffic from your application reaches it over the internet. Private Endpoints change that: they give the service a private IP address inside your VNet so traffic stays entirely on the Azure backbone and never goes out to the public internet.

I put together a step-by-step reference with validation checks and service-specific notes on my docs site. This post covers the thinking behind the feature: why it exists, where it earns its complexity, and what to watch out for.

What is a Private Endpoint?

A Private Endpoint is a network interface with a private IP address from your VNet's address space. It represents a specific PaaS resource (a storage account, a database, a key vault) and makes that resource reachable as if it were just another VM on your private network.

Under the hood, Azure creates a Network Interface Card (NIC) in your chosen subnet and maps it to the target resource. DNS is then updated so that the service's public FQDN resolves to the private IP instead of the public one.

The result: your application connects to the same FQDN it always has, but the traffic now flows privately within your VNet.

Why This Matters

There are three practical reasons to use Private Endpoints:

Reduced attack surface: Public endpoints are reachable by anyone on the internet. Even with strong authentication, you are exposing a target. A private endpoint removes that target entirely for callers inside your trusted network.

Network-level enforcement: You can disable public access on the service entirely after the private endpoint is in place. This means a misconfigured application or leaked credential cannot be exploited from outside your network.

Compliance: Many security frameworks and internal policies require that sensitive data services (databases, key vaults, storage) are not publicly accessible. Private Endpoints are the standard Azure mechanism to satisfy this requirement.

Why Not Just Use Firewall Rules and VNet Integration?

This is the most common pushback, and it is a fair question. VNet integration and service firewall rules are built into most Azure PaaS services, they are quick to configure, and they feel like the obvious first move.

The short version: they restrict who can call the service, but the service is still publicly addressable. The DNS name still resolves to a public IP. Anyone with a valid credential can attempt a connection from outside your network. A misconfigured firewall rule, an overly broad IP range, or a "temporary" public access opening for debugging can quietly leave things exposed in ways that are easy to miss.

There is also a subtler issue. VNet integration for services like App Service or Azure Functions routes outbound traffic into your VNet - it does not put the service itself inside the network. It controls where your app can reach out to, not where the service lives from the outside world's perspective.

Private Endpoints work differently. They move the service into your network at the IP level. The public endpoint still exists until you explicitly disable it, but once you do, the service is genuinely off the internet; not just guarded by rules that could be changed, misconfigured, or inherited from a template someone wrote two years ago.

The practical difference: firewall rules reduce risk, Private Endpoints change the architecture. Both have a place, but for anything carrying sensitive data, the architectural change is worth the extra setup.

The Three Parts You Cannot Skip

A common mistake is to create the endpoint and assume you're done. A working private endpoint setup always requires three things:

Component	What it does	What breaks without it
Private Endpoint	Creates the private NIC in your subnet	Nothing. This is the starting point
Private DNS Zone	Makes the FQDN resolve to the private IP	DNS resolves to the public IP; traffic bypasses the endpoint
Disabled public access	Removes the public path entirely	The endpoint is private, but the public path still exists

Missing DNS configuration is the most common reason private endpoint implementations fail. The endpoint exists, the subnet is correct, but nslookup still returns a public IP because the DNS zone was never linked to the VNet.

Things to Watch Out For

Private Endpoints are worth the effort, but they do introduce complexity that can catch you off guard if you are not expecting it.

On-premises and hybrid networks need extra thought. DNS is the most common place this surfaces. If your on-premises DNS servers do not know about Azure's private DNS zones, name resolution breaks for anything connecting from outside the VNet. Even if the endpoint itself is configured correctly. The fix (a DNS forwarder or conditional forwarding rules) is well-documented, but it is not automatic, and it is the kind of thing that gets missed until someone in a remote office or a VPN-connected machine suddenly cannot reach a service.

Development environments get more complicated. Once a service is locked down to a private path, a developer working from their laptop can no longer hit it directly unless they are connected through a jump box, VPN, or a bastion host. That is the right trade-off for production, but it is worth designing for early. Teams that retrofit Private Endpoints onto an existing setup often hit this friction first.

Misconfiguration is quiet. The portal will happily show a green checkmark on your endpoint while traffic is still taking the public route, because DNS was not updated or the public path was never closed. This is not a reason to avoid Private Endpoints. It is a reason to validate after you set them up, not just trust that the wizard completed without errors.

None of this changes the recommendation. It just changes how you plan for it.

Conclusion

Private Endpoints are the right default for any Azure PaaS service handling sensitive data or internal workloads. They're not complicated to set up, but they do have three moving parts (the endpoint, the DNS zone link, and the public access policy) and all three need to be correct for the setup to work.

The pattern is the same regardless of service type: create the endpoint, link the DNS zone, validate from the calling host, then disable public access. Once you've done it once, it becomes routine.

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