4.1 Azure Private Link and Private Endpoints

📘Microsoft Azure Networking Solutions (AZ-700)

1. What Is Azure Private Link Service?

Microsoft Azure provides a feature called Private Link Service.

A Private Link Service allows you to publish your own Azure service (for example, an internal web application behind a Standard Load Balancer) privately to other networks using Private Endpoints.

It provides:

Private IP-based access
No exposure to the public internet
Secure and controlled connectivity
Integration across different VNets, subscriptions, tenants, and even on-premises environments

2. What Does “Integrate with On-Premises Clients” Mean?

It means:

Your company has:

An on-premises data center (physical servers inside your office)
A service hosted in Azure using Private Link Service

You want:

On-premises users or servers to access that Azure service
Without using public internet
Using private IP addresses only

This requires hybrid network connectivity.

3. High-Level Architecture

To integrate Private Link Service with on-premises clients, you need:

Azure Virtual Network (VNet)
Private Link Service
Private Endpoint
Hybrid connectivity (VPN or ExpressRoute)
DNS configuration

Let’s break each one clearly.

4. Required Components Explained

4.1 Azure Virtual Network (VNet)

A VNet is your private network in Azure.

The Private Link Service must be deployed inside a VNet.

4.2 Private Link Service

A Private Link Service:

Is created behind a Standard Azure Load Balancer
Exposes a service privately
Can be consumed using Private Endpoints

Important exam point:

Private Link Service requires Standard Load Balancer
It does NOT work with Basic Load Balancer

4.3 Private Endpoint

A Private Endpoint:

Is a network interface with a private IP
Connects to a Private Link Service
Is deployed in a VNet

For on-premises access:

The Private Endpoint must be reachable from on-premises via hybrid connection

4.4 Hybrid Connectivity (Very Important for Exam)

To allow on-premises clients to reach Azure private IP addresses, you must configure:

Option 1: Site-to-Site VPN

Uses:

VPN Gateway in Azure
IPsec tunnel over internet
Secure connection

Option 2: ExpressRoute

Uses:

Private dedicated connection
Higher performance
More reliable
No internet exposure

Both allow:

On-premises network to access Azure private IP addresses

Exam Tip:
If question mentions high bandwidth, low latency, private connectivity, answer is usually ExpressRoute.

5. Step-by-Step Integration Process

Now let’s explain how everything works together.

Step 1: Create Azure VNet

Create a VNet
Create subnets
Ensure subnet has enough IP addresses

Step 2: Deploy Standard Load Balancer

Private Link Service must:

Be associated with Standard Load Balancer frontend
Use internal frontend IP

This load balancer routes traffic to backend services.

Step 3: Create Private Link Service

When creating:

Select Standard Load Balancer frontend IP
Choose NAT IP configuration
Configure auto-approval or manual approval

Important:
You can restrict which subscriptions can connect.

Step 4: Create Private Endpoint

Create a Private Endpoint in a VNet
Connect it to the Private Link Service
Get a private IP address

If in different subscription or tenant:

Connection request must be approved

Step 5: Configure Hybrid Connectivity

Set up either:

Site-to-Site VPN:

Create Azure VPN Gateway
Configure Local Network Gateway
Configure IPsec connection

ExpressRoute:

Create ExpressRoute circuit
Connect to Azure VNet using ExpressRoute Gateway

Now on-premises network can route traffic to Azure private IP ranges.

Step 6: Configure Routing

Make sure:

On-premises router has route to Azure VNet address space
Azure VNet has route back to on-premises network
Network Security Groups allow traffic

If routing is incorrect, traffic will fail.

6. DNS Configuration (Critical for Exam)

DNS is often tested in AZ-700.

On-premises clients usually connect using FQDN (for example: app.company.internal).

You must ensure:

DNS resolves to Private Endpoint IP
Not to public IP

Options:

Option 1: Use Azure Private DNS Zone

Create Private DNS Zone
Link it to VNet
Create A record pointing to Private Endpoint IP

Option 2: Forward DNS to Azure

If using on-premises DNS server:

Configure Conditional Forwarder
Forward specific zone to Azure DNS server
Azure resolves Private Endpoint IP

Exam scenario:
If on-premises users cannot access service but VPN works → usually DNS misconfiguration.

7. Traffic Flow Explanation (Very Important)

When on-premises client connects:

Client sends request to FQDN
DNS resolves to Private Endpoint IP
Traffic travels through:
- VPN or ExpressRoute
Enters Azure VNet
Reaches Private Endpoint
Private Endpoint forwards traffic to:
- Private Link Service
Load Balancer forwards traffic to backend servers

No public internet is used.

8. Security Considerations

Private Link improves security by:

Removing public exposure
Reducing attack surface
Using private IP communication
Enforcing approval process

You can also use:

Network Security Groups (NSG)
Azure Firewall
User Defined Routes (UDR)

Exam Tip:
Private Link does NOT replace:

NSG
Firewall
It works together with them.

9. Common Exam Scenarios

Scenario 1:

On-premises clients cannot reach Private Endpoint IP.
Check:

VPN/ExpressRoute connection
Routing tables
NSG rules

Scenario 2:

DNS resolves to public IP instead of private IP.
Solution:

Configure Private DNS zone
Configure conditional forwarder

Scenario 3:

Private Endpoint is in different subscription.
Solution:

Approve connection manually

Scenario 4:

Need highly secure, private access from branch offices.
Best choice:

ExpressRoute + Private Link

10. Important Limitations

For AZ-700 exam, remember:

Private Link Service requires Standard Load Balancer
Private Endpoint is region-specific
You cannot move Private Endpoint between VNets
Private Endpoint uses one private IP from subnet
Hybrid connectivity required for on-premises access
DNS configuration is mandatory for proper name resolution

11. Comparison: VPN vs ExpressRoute (For Exam)

Feature	VPN	ExpressRoute
Uses Internet	Yes (encrypted)	No
Performance	Moderate	High
SLA	Lower	Higher
Cost	Lower	Higher
Enterprise-scale	Limited	Recommended

12. Why This Topic Is Important for AZ-700

Microsoft tests:

Hybrid network design
Secure private access
DNS integration
Routing understanding
Private connectivity architecture

If you understand:

Private Link Service
Private Endpoint
VPN/ExpressRoute
DNS configuration
Routing

You can answer most exam questions from this section.

Final Summary

To integrate a Private Link Service with on-premises clients:

Deploy service behind Standard Load Balancer
Create Private Link Service
Create Private Endpoint
Establish hybrid connectivity (VPN or ExpressRoute)
Configure routing
Configure DNS properly
Secure with NSG and firewall

This ensures:

Secure private communication
No public exposure
Hybrid cloud connectivity
Enterprise-level architecture