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Difficulty: Very hardConfigure Azure DNS Private and Public Zones

Your company has an Azure subscription containing three virtual networks named VNetA, VNetB, and VNetC. VNetA is peered with VNetB, and VNetB is peered with VNetC. There is no direct peering between VNetA and VNetC. You create two Azure Private DNS zones named corp.contoso.com and dev.local. Virtual machines are deployed in all three virtual networks. You need to implement a DNS configuration that meets the following requirements:
- Virtual machines in VNetA must automatically register their DNS records in corp.contoso.com.
- Virtual machines in VNetB must automatically register their DNS records in dev.local.
- Virtual machines in VNetB and VNetC must be able to resolve DNS names in corp.contoso.com.
- Virtual machines in VNetC must be able to resolve DNS names in dev.local.

Which two virtual network link configurations should you perform to meet these requirements? (Select two.)

  1. Configure a virtual network link from corp.contoso.com to VNetA with auto-registration enabled, and configure virtual network links from corp.contoso.com to VNetB and VNetC with auto-registration disabled.Answer
  2. Configure a virtual network link from dev.local to VNetB with auto-registration enabled, and configure a virtual network link from dev.local to VNetC with auto-registration disabled.Answer
  3. C
    Configure virtual network links from both corp.contoso.com and dev.local to VNetB with auto-registration enabled.
  4. D
    Configure a virtual network link from corp.contoso.com to VNetA with auto-registration enabled, and rely on the existing virtual network peering to transitively resolve DNS names from VNetB and VNetC.
  5. E
    Configure a virtual network link from dev.local to VNetB with auto-registration enabled, and configure a virtual network link from dev.local to VNetA with auto-registration enabled.

Answer

Configure a virtual network link from corp.contoso.com to VNetA with auto-registration enabled, and configure virtual network links from corp.contoso.com to VNetB and VNetC with auto-registration disabled. Also, configure a virtual network link from dev.local to VNetB with auto-registration enabled, and configure a virtual network link from dev.local to VNetC with auto-registration disabled.
To satisfy the requirements, the virtual networks must be linked directly to the private DNS zones. Because VNetA must auto-register in corp.contoso.com, its link to that zone must have auto-registration enabled. Since VNetB must auto-register in dev.local, its link to dev.local must have auto-registration enabled. The remaining resolution requirements (VNetB and VNetC resolving corp.contoso.com, and VNetC resolving dev.local) must be met using links with auto-registration disabled, as a virtual network cannot have auto-registration enabled for more than one zone. Since DNS resolution is not transitive over virtual network peering, direct links with auto-registration disabled are required for VNetC to resolve both zones, and for VNetB to resolve corp.contoso.com.

Step-by-Step Solution

1
Determine the auto-registration requirements for each virtual network.
Identify that VNetA must register in corp.contoso.com, and VNetB must register in dev.local.
Azure Private DNS allows a virtual network to be linked to only one private DNS zone with auto-registration enabled.
2
Determine the DNS resolution requirements for each virtual network.
Identify that VNetB and VNetC require name resolution for corp.contoso.com, and VNetC requires name resolution for dev.local.
DNS resolution is not transitive across peered virtual networks. Each VNet that requires name resolution must have an explicit virtual network link to the Private DNS zone.
3
Define the link types (registration vs. resolution-only) for each zone and VNet.
Create registration links for corp.contoso.com to VNetA, and dev.local to VNetB. Create resolution-only links (auto-registration disabled) for corp.contoso.com to VNetB and VNetC, and for dev.local to VNetC.
This satisfies all auto-registration and resolution requirements while adhering to the one-registration-link limit per VNet and ensuring all networks can resolve target zones.

Key Concept

Azure Private DNS Virtual Network Links and Auto-registration Constraints
Estimated Time:3m 0s
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Topics

Configure Azure DNS Private and Public Zones

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