Azure Networking

Azure networking services enable you to create secure, scalable, and highly available networks in the cloud. These services include foundational components like Virtual Networks and more advanced solutions for security, load balancing, and connectivity.

Azure Virtual Network (VNet) is the foundational building block for your private network in Azure. It enables Azure resources to securely communicate with each other, with the internet, and with your on-premises networks.

• Isolation: VNets provide network isolation for your cloud resources.
• Address Space: You define a private IP address space for your VNet.
• Connectivity: Enables communication between Azure resources, on-premises networks, and the internet.

Subnets allow you to segment your VNet's address space into smaller ranges. This helps in organizing resources and applying network policies at a granular level.

• Segmentation: Divides a VNet into smaller IP address ranges.
• Security: Allows for the application of Network Security Groups (NSGs) to control traffic flow.
• Resource Grouping: Helps in grouping related resources.

A Network Interface (NIC) connects an Azure resource, such as a virtual machine, to a VNet. Each NIC can have one or more private and public IP addresses.

• Connection: Acts as the network adapter for Azure resources.
• IP Configuration: Allows association with IP addresses.
• Security: Can be associated with Network Security Groups (NSGs) and Application Security Groups (ASGs).

Azure provides both public and private IP addresses. Public IPs are used to communicate with resources over the internet, while private IPs are used for communication within your VNet and connected networks.

• Public IP Addresses: For internet-facing services.
• Private IP Addresses: For internal communication.
• Static vs. Dynamic: IP addresses can be assigned statically or dynamically.

Network Security Groups (NSGs) act as a virtual firewall for your Azure resources to help filter network traffic. You can associate NSGs with NICs or subnets.

• Inbound/Outbound Rules: Define rules to allow or deny traffic based on source/destination IP address, port, and protocol.
• Priority: Rules are processed in order of priority.
• Stateful: NSGs are stateful; if you allow inbound traffic, the outbound reply is automatically allowed.

For more advanced security filtering, consider Azure Firewall or Application Gateway.

User-defined route tables allow you to override Azure's default system routes. This is useful for forcing traffic through a network virtual appliance (NVA) or for more complex routing scenarios.

• Custom Routes: Define custom routes for subnets.
• Next Hop Types: Can specify VNet gateway, virtual appliance, or Internet as the next hop.
• Propagation: Routes can be propagated from on-premises gateways.

Azure Load Balancer distributes incoming network traffic across a pool of backend resources. It operates at Layer 4 (TCP/UDP) and can be used for both internal and external traffic.

• High Availability: Distributes traffic to ensure services remain available.
• Scalability: Allows you to scale your applications by adding more backend instances.
• Health Probes: Monitors the health of backend instances and directs traffic only to healthy ones.

For Layer 7 load balancing with features like SSL offloading and web application firewall (WAF), consider Azure Application Gateway.

Azure Firewall is a cloud-native, intelligent network firewall that protects your virtual network resources. It's a fully stateful firewall as a service with high availability and unrestricted cloud scalability.

• Centralized Protection: Provides a single point of defense for your VNet.
• Network & Application Rules: Supports filtering based on IP addresses, ports, protocols, and fully qualified domain names (FQDNs).
• Threat Intelligence: Integrates with Azure threat intelligence feeds.

Azure Application Gateway is a web traffic load balancer that enables you to manage traffic to your web applications. It offers Layer 7 load balancing, SSL termination, cookie-based session affinity, and Web Application Firewall (WAF).

• Layer 7 Load Balancing: Routes traffic based on URL paths, host headers, etc.
• SSL Termination: Decrypts SSL/TLS traffic at the gateway, reducing the load on backend servers.
• Web Application Firewall (WAF): Protects web applications from common web exploits.

Azure VPN Gateway allows you to send encrypted traffic between your on-premises data center and Azure, or between your Azure VNets. This is typically done using IPsec/IKE VPN tunnels.

• Site-to-Site VPN: Connects your on-premises network to Azure.
• VNet-to-VNet VPN: Connects multiple Azure VNets securely.
• Point-to-Site VPN: Connects individual client devices to Azure.

Azure ExpressRoute enables you to create private connections between Azure datacenters and infrastructure that is either on-premises or in a colocation environment. This offers higher bandwidth, lower latencies, and increased reliability compared to standard internet connections.

• Private Connectivity: Dedicated, private connections.
• High Bandwidth & Low Latency: Ideal for large data transfers and latency-sensitive applications.
• Reliability: Offers higher uptime and performance guarantees.