AZ-104 Objective 4.3: Configure Name Resolution and Load Balancing

September 14, 2025•45 min read•Microsoft Azure Administrator

AZ-104 Exam Focus: This objective covers Azure DNS configuration and load balancing services. Understanding DNS management, internal and public load balancers, and load balancing troubleshooting is crucial for Azure administrators managing network services and application availability. Master these concepts for both exam success and real-world Azure network service management.

Understanding Name Resolution and Load Balancing in Azure

Name resolution and load balancing are fundamental network services that ensure reliable connectivity and high availability for applications. Azure provides comprehensive DNS services and multiple load balancing options to meet different requirements. These services work with Azure Virtual Networks and integrate with Azure App Service for web application hosting.

Key Components

Azure DNS: Hosted DNS service for domain name resolution
Azure Load Balancer: Layer 4 load balancing for TCP/UDP traffic
Application Gateway: Layer 7 load balancing with advanced features
Traffic Manager: DNS-based global load balancing
Front Door: Global CDN and load balancing service

1. Configure Azure DNS

Azure DNS is a hosting service for DNS domains that provides name resolution using Microsoft's Azure infrastructure. It offers high availability, security, and performance for your DNS queries.

Azure DNS Features

Core Capabilities:

High Availability: 99.99% SLA with global distribution
Fast Resolution: Low-latency DNS queries worldwide
Security: Built-in DDoS protection and DNSSEC support
Integration: Seamless integration with Azure services
Private DNS: Private DNS zones for internal resolution
Alias Records: Point to Azure resources with automatic updates

Creating DNS Zones

# Create public DNS zone
az network dns zone create \
  --name mydomain.com \
  --resource-group myResourceGroup

# Create private DNS zone
az network dns zone create \
  --name mydomain.local \
  --resource-group myResourceGroup \
  --zone-type Private

# Link private DNS zone to VNet
az network private-dns link vnet create \
  --name myDNSLink \
  --resource-group myResourceGroup \
  --zone-name mydomain.local \
  --virtual-network myVNet \
  --registration-enabled true

Creating DNS Records

# Create A record
az network dns record-set a add-record \
  --resource-group myResourceGroup \
  --zone-name mydomain.com \
  --record-set-name www \
  --ipv4-address 10.0.1.4

# Create CNAME record
az network dns record-set cname set-record \
  --resource-group myResourceGroup \
  --zone-name mydomain.com \
  --record-set-name blog \
  --cname blog.mydomain.com

# Create MX record
az network dns record-set mx add-record \
  --resource-group myResourceGroup \
  --zone-name mydomain.com \
  --record-set-name @ \
  --exchange mail.mydomain.com \
  --preference 10

# Create alias record (points to Azure resource)
az network dns record-set a create \
  --resource-group myResourceGroup \
  --zone-name mydomain.com \
  --name www \
  --target-resource /subscriptions/{subscription-id}/resourceGroups/myResourceGroup/providers/Microsoft.Network/publicIPAddresses/myPublicIP

DNS Record Types

Record Type	Purpose	Example	Notes
A	IPv4 address	www.mydomain.com → 10.0.1.4	Most common record type
AAAA	IPv6 address	www.mydomain.com → 2001:db8::1	IPv6 support
CNAME	Canonical name	blog.mydomain.com → www.mydomain.com	Cannot use with root domain
MX	Mail exchange	mydomain.com → mail.mydomain.com	Email routing
TXT	Text record	Domain verification, SPF	Verification and policies

2. Configure an Internal or Public Load Balancer

Azure Load Balancer provides high availability and network performance for your applications by distributing incoming traffic across multiple VMs or service instances.

Load Balancer Types

Load Balancer SKUs:

Basic: Free tier with basic features
Standard: Advanced features with higher SLA
Public: Internet-facing load balancer
Internal: Private load balancer within VNet

Creating a Public Load Balancer

# Create public IP for load balancer
az network public-ip create \
  --name myLoadBalancerPublicIP \
  --resource-group myResourceGroup \
  --location eastus \
  --sku Standard \
  --allocation-method Static

# Create public load balancer
az network lb create \
  --name myPublicLoadBalancer \
  --resource-group myResourceGroup \
  --location eastus \
  --sku Standard \
  --public-ip-address myLoadBalancerPublicIP

# Create backend address pool
az network lb address-pool create \
  --name myBackendPool \
  --resource-group myResourceGroup \
  --lb-name myPublicLoadBalancer

# Create health probe
az network lb probe create \
  --name myHealthProbe \
  --resource-group myResourceGroup \
  --lb-name myPublicLoadBalancer \
  --protocol Http \
  --port 80 \
  --path /health

# Create load balancing rule
az network lb rule create \
  --name myLoadBalancerRule \
  --resource-group myResourceGroup \
  --lb-name myPublicLoadBalancer \
  --protocol Tcp \
  --frontend-port 80 \
  --backend-port 80 \
  --frontend-ip-name LoadBalancerFrontEnd \
  --backend-pool-name myBackendPool \
  --probe-name myHealthProbe

Creating an Internal Load Balancer

# Create internal load balancer
az network lb create \
  --name myInternalLoadBalancer \
  --resource-group myResourceGroup \
  --location eastus \
  --sku Standard \
  --vnet-name myVNet \
  --subnet mySubnet \
  --private-ip-address 10.0.1.100

# Create backend address pool
az network lb address-pool create \
  --name myInternalBackendPool \
  --resource-group myResourceGroup \
  --lb-name myInternalLoadBalancer

# Create health probe
az network lb probe create \
  --name myInternalHealthProbe \
  --resource-group myResourceGroup \
  --lb-name myInternalLoadBalancer \
  --protocol Tcp \
  --port 80

# Create load balancing rule
az network lb rule create \
  --name myInternalLoadBalancerRule \
  --resource-group myResourceGroup \
  --lb-name myInternalLoadBalancer \
  --protocol Tcp \
  --frontend-port 80 \
  --backend-port 80 \
  --frontend-ip-name LoadBalancerFrontEnd \
  --backend-pool-name myInternalBackendPool \
  --probe-name myInternalHealthProbe

Load Balancer Configuration Options

Feature	Basic SKU	Standard SKU
Availability Zones	No	Yes
HA Ports	No	Yes
Outbound Rules	No	Yes
Multiple Frontend IPs	No	Yes
Diagnostics	Limited	Full

Load Balancing Rules and Distribution

Distribution Methods:

5-tuple Hash: Source IP, source port, destination IP, destination port, protocol
3-tuple Hash: Source IP, destination IP, destination port
Source IP Affinity: Sticky sessions based on source IP
Session Persistence: Maintain client connections to same backend

Health Probes

# Create HTTP health probe
az network lb probe create \
  --name myHTTPProbe \
  --resource-group myResourceGroup \
  --lb-name myLoadBalancer \
  --protocol Http \
  --port 80 \
  --path /health \
  --interval 15 \
  --threshold 2

# Create TCP health probe
az network lb probe create \
  --name myTCPProbe \
  --resource-group myResourceGroup \
  --lb-name myLoadBalancer \
  --protocol Tcp \
  --port 80 \
  --interval 15 \
  --threshold 2

# Create HTTPS health probe
az network lb probe create \
  --name myHTTPSProbe \
  --resource-group myResourceGroup \
  --lb-name myLoadBalancer \
  --protocol Https \
  --port 443 \
  --path /health \
  --interval 15 \
  --threshold 2

3. Troubleshoot Load Balancing

Load balancing troubleshooting involves identifying connectivity issues, health probe failures, and traffic distribution problems. Understanding common issues and diagnostic tools is essential for maintaining service availability.

Common Load Balancing Issues

Troubleshooting Checklist:

Check health probe configuration and responses
Verify backend pool member status
Validate load balancing rules and port configuration
Check NSG rules for load balancer traffic
Verify backend server application health
Test connectivity from different sources
Review load balancer metrics and logs

Load Balancer Diagnostics

# Check load balancer status
az network lb show \
  --name myLoadBalancer \
  --resource-group myResourceGroup \
  --query "provisioningState"

# List backend pool members
az network lb address-pool show \
  --name myBackendPool \
  --resource-group myResourceGroup \
  --lb-name myLoadBalancer

# Check health probe status
az network lb probe show \
  --name myHealthProbe \
  --resource-group myResourceGroup \
  --lb-name myLoadBalancer

# Test connectivity to load balancer
az network watcher test-connectivity \
  --resource-group myResourceGroup \
  --source-resource myVM \
  --dest-address myLoadBalancerPublicIP \
  --dest-port 80

# Check load balancer metrics
az monitor metrics list \
  --resource /subscriptions/{subscription-id}/resourceGroups/myResourceGroup/providers/Microsoft.Network/loadBalancers/myLoadBalancer \
  --metric "DipAvailability"

Health Probe Troubleshooting

Probe Issues:

Probe Failing: Check if application responds on probe port/path
Wrong Path: Verify health check endpoint exists
Port Issues: Ensure application listens on probe port
NSG Blocking: Check NSG rules allow probe traffic
Application Errors: Verify application returns HTTP 200
Timeout Issues: Adjust probe interval and threshold

Backend Pool Troubleshooting

# Add VM to backend pool
az network nic ip-config address-pool add \
  --resource-group myResourceGroup \
  --nic-name myNIC \
  --ip-config-name ipconfig1 \
  --lb-name myLoadBalancer \
  --address-pool myBackendPool

# Remove VM from backend pool
az network nic ip-config address-pool remove \
  --resource-group myResourceGroup \
  --nic-name myNIC \
  --ip-config-name ipconfig1 \
  --lb-name myLoadBalancer \
  --address-pool myBackendPool

# Check backend pool member health
az network lb show \
  --name myLoadBalancer \
  --resource-group myResourceGroup \
  --query "backendAddressPools[0].backendIPConfigurations[0].provisioningState"

Load Balancer Monitoring

Key Metrics:

Data Path Availability: Overall load balancer health
Health Probe Status: Backend pool member health
SNAT Connection Count: Outbound connection usage
Byte Count: Data processed by load balancer
Packet Count: Network packets processed
SYN Count: TCP connection attempts

Advanced Load Balancing Features

Outbound Rules (Standard SKU)

# Create outbound rule
az network lb outbound-rule create \
  --name myOutboundRule \
  --resource-group myResourceGroup \
  --lb-name myLoadBalancer \
  --frontend-ip-configs myFrontendIPConfig \
  --backend-pool myBackendPool \
  --protocol All \
  --idle-timeout 4 \
  --allocated-outbound-ports 1024

HA Ports (Standard SKU)

# Create HA ports rule
az network lb rule create \
  --name myHAPortsRule \
  --resource-group myResourceGroup \
  --lb-name myLoadBalancer \
  --protocol All \
  --frontend-port 0 \
  --backend-port 0 \
  --frontend-ip-name LoadBalancerFrontEnd \
  --backend-pool-name myBackendPool \
  --probe-name myHealthProbe

DNS and Load Balancer Integration

# Create alias record pointing to load balancer
az network dns record-set a create \
  --resource-group myResourceGroup \
  --zone-name mydomain.com \
  --name www \
  --target-resource /subscriptions/{subscription-id}/resourceGroups/myResourceGroup/providers/Microsoft.Network/loadBalancers/myLoadBalancer

# Create CNAME record for load balancer
az network dns record-set cname set-record \
  --resource-group myResourceGroup \
  --zone-name mydomain.com \
  --record-set-name api \
  --cname myLoadBalancer.eastus.cloudapp.azure.com

Exam Tips and Key Points

Critical Exam Knowledge:

Azure DNS: Understand zone types, record types, and alias records
Load Balancer SKUs: Know differences between Basic and Standard
Health Probes: Understand probe types and configuration
Distribution Methods: Know hash-based and affinity options
Troubleshooting: Understand common issues and diagnostic tools
Integration: Know how DNS and load balancers work together
Monitoring: Understand key metrics and logging

Common Scenarios and Solutions

Real-World Scenarios:

Web Application Load Balancing: Use public load balancer with HTTP health probes
Database Load Balancing: Use internal load balancer for database tier
Multi-Region DNS: Use Azure DNS with Traffic Manager for global distribution
Session Persistence: Configure source IP affinity for stateful applications
High Availability: Use Standard SKU with availability zones
Outbound Connectivity: Configure outbound rules for backend servers

Summary

Name resolution and load balancing are essential services for maintaining application availability and performance. This objective covers the key aspects of Azure DNS and load balancing:

Azure DNS configuration for public and private zones
Load balancer creation and configuration for internal and public scenarios
Health probe configuration and monitoring
Load balancing troubleshooting and diagnostics
Integration between DNS and load balancing services
Advanced features like outbound rules and HA ports

Understanding these services is essential for Azure administrators to design, implement, and maintain highly available and performant network architectures in Azure environments.

Next Steps: Practice creating DNS zones, configuring load balancers, and setting up health probes in the Azure portal. Experiment with different load balancing scenarios and troubleshoot common issues to understand the complete DNS and load balancing ecosystem in Azure.