DNS

🌐 What is Azure DNS?¶

Azure DNS is a Domain Name System (DNS) hosting service that lets you host your DNS domains and manage DNS records using Azure infrastructure.

It translates human-readable domain names (like myapp.com) into IP addresses (like 52.161.10.5) to route traffic properly.

📚 Table of Contents¶

What is DNS? (Quick Recap)
What is Azure DNS?
Key Features
Azure DNS Types
Supported DNS Record Types
Hands-On Setup (Portal & CLI)
Custom Domain Mapping (Azure Web Apps)
Azure Private DNS
Best Practices
Interview Questions

1️⃣ What is DNS? (Quick Recap)¶

DNS = Phonebook of the internet
Maps domain names to IP addresses
Works with recursive and authoritative name servers

2️⃣ What is Azure DNS?¶

Azure DNS allows you to:

Host public or private DNS zones
Manage DNS records with Azure CLI, PowerShell, REST
Use role-based access control (RBAC) and activity logs

✅ Low latency
✅ Global reach
✅ Secure & reliable

3️⃣ Key Features¶

Feature	Description
Public & Private DNS Zones	Support for internal and external name resolution
Record Management	A, AAAA, CNAME, MX, TXT, etc.
Azure Integration	VMs, App Services, Traffic Manager
Role-based Access	Control DNS using Azure RBAC
Fast Resolution	Powered by Azure’s global network of name servers
Monitoring	Activity logs, alerts, diagnostics

4️⃣ Azure DNS Types¶

Type	Description	Use Case
Public DNS Zone	DNS zone accessible from internet	Host public website or API
Private DNS Zone	Internal-only DNS within a VNet	Resolve internal VM names securely

5️⃣ Supported DNS Record Types¶

Record Type	Description	Example
A	Maps name to IPv4	`app.contoso.com` → `192.168.1.1`
AAAA	Maps name to IPv6	`app.contoso.com` → `2607:f8b0::1`
CNAME	Alias to another domain	`www.contoso.com` → `contoso.com`
MX	Mail server	For email routing
TXT	Text data	SPF, DKIM
NS	Name server	Delegation of zones
PTR	Reverse DNS	IP to domain name
SRV	Service location	Skype, LDAP

6️⃣ Hands-On: Create a Public DNS Zone¶

✅ Azure Portal¶

Go to DNS Zones → Create
Enter:
- Name: example.com
- Resource group
Create records (e.g., A, CNAME)

💻 Azure CLI¶

# Create a DNS zone
az network dns zone create \
  --name example.com \
  --resource-group myRG

# Create an A record
az network dns record-set a add-record \
  --zone-name example.com \
  --resource-group myRG \
  --record-set-name www \
  --ipv4-address 52.160.10.10

# Create a CNAME record
az network dns record-set cname set-record \
  --zone-name example.com \
  --resource-group myRG \
  --record-set-name blog \
  --cname contoso.azurewebsites.net

7️⃣ Custom Domain Mapping (e.g., for App Service)¶

If you're using Azure Web App (app.azurewebsites.net) and want to map www.myapp.com:

Add a CNAME record in Azure DNS:
```
www → app.azurewebsites.net
```
Go to App Service → Custom domains → Add www.myapp.com
Validate DNS & bind it.

8️⃣ Azure Private DNS Zones¶

Feature	Description
Internal-only name resolution
Uses VNet link to associate
Automatically resolves Azure VM names
No need for custom DNS servers

Example:¶

Create private zone: internal.contoso.com
Link it to your VNet
Add A record: web1 → 10.1.1.4
VMs in the VNet can now use web1.internal.contoso.com

9️⃣ Best Practices¶

Practice	Why
Use Azure DNS for global reliability	Fast resolution using Azure’s DNS infrastructure
Use CNAME for web apps	Easier to change endpoints
Use Private DNS for internal services	Secure name resolution inside VNets
Use RBAC	Control who can edit DNS records
Enable DNS zone logging	Audit and monitor changes