Jeff’s Insights #
“Unlike generic exam dumps, Jeff’s Insights is designed to make you think like a Real-World Production Architect. We dissect this scenario by analyzing the strategic trade-offs required to balance operational reliability, security, and long-term cost across multi-service deployments.”
While preparing for the AZ-104 Azure Administrator exam, many candidates struggle with proper configuration of Azure Private DNS zones and automatic DNS registration for VMs in hybrid or cloud-only virtual networks. In the enterprise world, these decisions often hinge on ensuring seamless name resolution without compromising private network isolation and governance. Let’s drill into a simulated enterprise hybrid networking scenario.
The Architecture Drill (Simulated Question) #
Scenario #
Tailspin Solutions is a multinational enterprise undergoing digital transformation to modernize its legacy datacenters by migrating workloads to Azure. They run several Windows Server 2019 VMs inside their Azure virtual network called VNET1.
The networking team needs to implement an internal DNS strategy that leverages Azure Private DNS zones. They plan to create a private DNS zone named prod.tailspin.com, scoped to the VNET1 virtual network to allow virtual machines to register their IP addresses automatically within this zone.
Currently, VM1 in VNET1 is configured with both a private IP address and a public IP address.
The Requirement: #
Ensure that VM1 automatically registers the correct A records in the prod.tailspin.com Private DNS zone, enabling consistent internal name resolution for hybrid workloads without exposing internal IP addresses publicly.
Which A record(s) will VM1 add to the prod.tailspin.com private DNS zone under this configuration?
The Options #
- A) VM1 will have no A record in the private DNS zone.
- B) VM1 will register only its private IP address in the private DNS zone.
- C) VM1 will register only its public IP address in the private DNS zone.
- D) VM1 will register both its private and public IP addresses in the private DNS zone.
Correct Answer #
B) VM1 will register only its private IP address in the private DNS zone.
The Architect’s Analysis #
Correct Answer #
Option B: VM1 only registers its private IP address in the prod.tailspin.com Azure Private DNS zone.
The Winning Logic #
Azure Private DNS zones, when linked to a virtual network and configured for auto-registration, only register the private IP addresses of VMs within that virtual network. This enables reliable internal name resolution without exposing public IP addresses on internal DNS zones, which is a critical security and governance consideration.
This design aligns with these pillars of Microsoft’s Well-Architected Framework (WAF):
- Security: Prevents accidental exposure of public IPs in private DNS zones, reducing attack surface.
- Reliability: Ensures internal workloads can reliably resolve names via private IPs.
- Operational Excellence: Automation of DNS registration reduces manual overhead and errors.
- Cost Optimization: Avoids unnecessary public DNS queries by leveraging internal private zones.
- Performance Efficiency: DNS queries resolve quickly within the boundary of the VNET.
The Trap (Distractor Analysis): #
- Why not A? Lack of any A record would break name resolution internally, defeating the purpose of auto-registration.
- Why not C? Public IPs are not registered in Private DNS zones; they remain external and resolved through public DNS.
- Why not D? Auto-registration does not add multiple IPs for a VM, only private ones in the linked VNET.
The Architect Blueprint #
Mermaid Diagram illustrating the DNS auto-registration flow for VMs into a Private DNS zone in a hybrid cloud setup:
Diagram Note: VM1 registers only its private IP automatically within the prod.tailspin.com Private DNS zone linked to VNET1, maintaining internal name resolution isolated from public DNS.
The Decision Matrix #
| Option | Est. Complexity | Est. Monthly Cost | Pros | Cons |
|---|---|---|---|---|
| A | Low | None | No DNS entries (simple but breaks resolution) | Fails requirement, no internal connectivity |
| B | Low | Minimal (DNS free) | Automatic private IP registration, secure & reliable | None |
| C | Medium | Potentially higher | Incorrectly registers public IPs, security risk | Public IPs exposed inside private zones |
| D | Medium | Higher | Both IPs registered, confusing for internal clients | Violates best practice, security risk |
Real-World Application (Practitioner Insight) #
Exam Rule #
“For the AZ-104 exam, always remember: Azure Private DNS zone auto-registration only publishes private IP address A records for VMs linked to the zone via virtual networks.”
Real World #
“In production hybrid cloud environments, this model ensures internal name resolution integrity and governance compliance. Public IPs are managed separately, ensuring hybrid workloads don’t inadvertently expose sensitive internal details.”
Disclaimer
This is a study note based on simulated scenarios for the AZ-104 exam. It is not an official question from Microsoft.