What is a virtual network link?

Question

Pulumi · Accepted Answer

A virtual network link establishes a relationship or connection between a private DNS zone and a virtual network, enabling name resolution from the virtual network. In other words, it allows resources within the virtual network to resolve domain names in a private DNS zone.

For example, in Microsoft Azure, you can create a private Azure DNS zone and then associate it with your virtual network using a "virtual network link". This allows VMs or other resources within that linked virtual network to resolve domain names using the private DNS zone.

This concept is useful when you have private resources within a virtual network and want to use custom domain names rather than the cloud provider's auto-generated ones. These domain names are only resolvable within the scope of the linked virtual network, providing security and isolation benefits for your workloads.

Here's an example of how you could create a virtual network and a private DNS zone with a virtual network link in Pulumi using the Azure provider. Let's setup an Azure virtual network (vnet) and a private DNS zone, then link them together:

```typescript
import * as pulumi from "@pulumi/pulumi";
import * as azure from "@pulumi/azure";

// Creating a resource group
const resourceGroup = new azure.core.ResourceGroup("resourceGroup", {
    location: "West Europe",
});

// Creating a virtual network
const network = new azure.network.VirtualNetwork("network", {
    resourceGroupName: resourceGroup.name,
    addressSpaces: ["10.0.0.0/16"]
});

// Creating a subnet within the virtual network
const subnet = new azure.network.Subnet("subnet", {
    resourceGroupName: resourceGroup.name,
    virtualNetworkName: network.name,
    addressPrefix: "10.0.1.0/24"
});

// Creating a private DNS zone
const privateZone = new azure.privateDns.Zone("privateZone", {
    resourceGroupName: resourceGroup.name,
    name: "privatezone.com"
});

// Creating a virtual network link between the DNS zone and virtual network
const zoneLink = new azure.privateDns.VirtualNetworkLink("zoneLink", {
    resourceGroupName: resourceGroup.name,
    zoneName: privateZone.name,
    virtualNetworkId: network.id,
    registrationEnabled: true,
});
```

In this example, we first create a resource group which is essentially a logical container for resources deployed on Azure. After that, we declare our virtual network and a subnet within that network.

Then, we create a private DNS zone.

Finally, using `azure.privateDns.VirtualNetworkLink`, we create a link between the DNS zone and the virtual network. The `registrationEnabled: true` property means that the DNS records can be registered automatically in the DNS zone for the virtual machines that are part of the given `virtualNetworkId`. This means any VMs within this network could resolve names using the private DNS zone.

This is an abstract explanation, in a real-world scenario, consider using appropriate CIDR ranges, names, and locations according to your need.