Difference between azure internal load balancer and external load balancer

 Azure Internal Load Balancer (ILB) and Azure External Load Balancer serve different purposes in managing network traffic within Microsoft Azure:

Azure Internal Load Balancer (ILB):

1. Traffic Type:
• Internal: ILB is designed to distribute network traffic within a virtual network, handling traffic that remains within Azure's private network.
2. Use Case:
• Internal Applications: ILB is used for balancing traffic to resources and services that are not exposed to the public internet, such as databases, internal web services, or application tiers.
3. IP Addressing:
• Private IP: ILB is associated with a private IP address (VIP - Virtual IP address) and routes traffic between resources within the virtual network.
4. Layer 4 Load Balancing:
• ILB operates at Layer 4 (Transport layer) of the OSI model, routing traffic based on TCP/UDP port and protocol. It does not inspect application content.
5. Session Persistence:
• It supports session affinity (sticky sessions) to route related traffic from a single client to the same backend resource for the duration of a session.

Azure External Load Balancer:

1. Traffic Type:
• External: External Load Balancer manages incoming internet traffic, acting as the entry point for applications and services exposed to the public internet.
2. Use Case:
• Public-Facing Services: External Load Balancer is used to distribute internet-facing traffic across multiple virtual machines (VMs) or instances for improved availability and scalability.
3. IP Addressing:
• Public IP: External Load Balancer is associated with a public IP address (VIP - Virtual IP address) that clients use to access applications and services from the internet.
4. Layer 4 Load Balancing:
• Similar to ILB, External Load Balancer operates at Layer 4 (Transport layer) and routes traffic based on TCP/UDP port and protocol. It does not inspect application content.
5. Session Persistence:
• It supports session affinity (sticky sessions) to ensure that related traffic from a single client is routed to the same backend resource for the duration of a session.

In summary, the key difference between Azure Internal Load Balancer and External Load Balancer is their focus on traffic type and use case. ILB is used for routing and load balancing internal network traffic within an Azure virtual network, while External Load Balancer is used for distributing incoming internet traffic to public-facing services and applications. Both provide high availability and fault tolerance but serve different networking scenarios.