# Custom DNS Support

### Task

Customers may choose to use their own DNS server instead of the default Azure-provided DNS for various reasons.

### Limitations of On-Prem DNS

By Microsoft’s design, only the Azure DNS server (168.63.129.16) can resolve Azure services (Storage account, Azure SQL, Azure Managed Redis, etc.) with their private IPs (example: 192.168.x.x / 172.16.x.x / 10.x.x.x).

Inforiver’s network setup is designed to communicate only using private IPs (Private endpoints) among its core resources within the deployed VNet. So, if there isn’t any existing service/configuration to forward Azure Private Link DNS queries to 168.63.129.16, the queries will either fail or resolve with public IPs where the communication can’t be made.

### How to Resolve? 

{% hint style="info" %}
We will only cover a few scenarios in this document. Your DNS setup and requirements may vary. For the complete list of supported scenarios and Microsoft-recommended approaches for each of them, please refer to: <https://learn.microsoft.com/en-us/azure/private-link/private-endpoint-dns-integration>
{% endhint %}

### Scenario I - Azure Private Resolver with on-premises DNS forwarder

#### Reference Architecture:

![](/files/edef4029031f318481ca4265fb200c84b76e7ebc)

{% stepper %}
{% step %}

### DNS private resolver rules

Add the following domain names to the ruleset and set the destination to your on-premises DNS IP & Port:

1. blob.core.windows.net
2. file.core.windows.net
3. redis.azure.net
4. database.windows.net
5. azurewebsites.net
6. vaultcore.azure.net

<figure><img src="/files/fzqOeZIcLfx3TlsXYuKx" alt=""><figcaption><p>Ruleset</p></figcaption></figure>
{% endstep %}

{% step %}

### Azure DNS IP should be added to the forwarders list

Add the Azure DNS IP (168.63.129.16) into the forwarders list of your on-prem DNS where appropriate.

<img src="/files/aa35a68b5ea96730639eb27e8000f709ddfca26f" alt="Add to Forwarders list" width="563">
{% endstep %}

{% step %}

### Create conditional forwarders to 168.63.129.16

Create conditional forwarders for the above domains listed in Step 1 and point them to the IP address 168.63.129.16.

<img src="/files/ac836500eeac2ce4b5d0f53741c2a73d500f2b64" alt="Conditional Forwarder" width="563">

#### Conditional Forwarders reference config:

<figure><img src="/files/59rWXJdyinPHV7dOt39j" alt=""><figcaption><p>Conditional Forwarders Reference Config</p></figcaption></figure>
{% endstep %}

{% step %}

### Establish Virtual Network Links

{% hint style="info" %}
:bulb: Important Note:&#x20;

The resolution is made by a private DNS zone [linked to a virtual network](https://learn.microsoft.com/en-us/azure/dns/private-dns-virtual-network-links). Make sure the Virtual Network links are established between the Azure Private DNS Zone(s) and the VNet where the VPN/ExpressRoute is connected.
{% endhint %}

#### Reference for privatelink.blob.core.windows.net:

![](/files/ed162e99a4a41d8cfd0b712666b01c053fcdad74)
{% endstep %}

{% step %}

### Validate

Validate DNS resolution using `nslookup` from the DNS server.

![Validate](/files/af67139c9e745c2fe80b7f7a1b4d876a01742c66)
{% endstep %}
{% endstepper %}

### References

1. **What is IP address 168.63.129.16?**

{% embed url="<https://learn.microsoft.com/en-us/azure/virtual-network/what-is-ip-address-168-63-129-16>" %}

2\. **Azure Private Endpoint DNS integration Scenarios**

{% embed url="<https://learn.microsoft.com/en-us/azure/private-link/private-endpoint-dns-integration>" %}

3. **What is a virtual network link?**

{% embed url="<https://learn.microsoft.com/en-us/azure/dns/private-dns-virtual-network-links>" %}


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