https://github.com/kolosovpetro/azureloadbalancerterraform
Gameplay with Azure Load Balancer and few Linux VMs
https://github.com/kolosovpetro/azureloadbalancerterraform
Last synced: 7 months ago
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Gameplay with Azure Load Balancer and few Linux VMs
- Host: GitHub
- URL: https://github.com/kolosovpetro/azureloadbalancerterraform
- Owner: kolosovpetro
- License: gpl-2.0
- Created: 2023-06-08T12:19:23.000Z (over 2 years ago)
- Default Branch: master
- Last Pushed: 2025-02-13T02:06:14.000Z (8 months ago)
- Last Synced: 2025-02-13T02:25:22.759Z (8 months ago)
- Language: HCL
- Homepage:
- Size: 51.8 KB
- Stars: 0
- Watchers: 1
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Azure Load Balancer
Azure Load Balancer (ALB) is a Layer 4 (TCP/UDP) service that distributes network traffic across multiple virtual
machines (VMs) to ensure availability and reliability.
## Infrastructure provision
- terraform plan
- terraform apply
- Deploy-Blue-Page.ps1
- Deploy-Green-Page.ps1
## What's done
- Blue backend pool: 1 linux vm
- Green backend pool: 1 linux vm
- SSH NAT rule: 44 -> blue slot vm 22
- SSH NAT rule: 45 -> green slot vm 22
- HTTP NAT rule: 81 -> green slot vm 80
- LB rule: 80 -> blue backend pool 80
---
## Main components of ALB
- **Frontend IP Configuration**: Defines the public or private IP used to accept incoming traffic to the load balancer.
- **Backend Pool**: A group of VMs or instances that receive traffic distributed by the load balancer.
- **Load Balancing Rule**: Defines how traffic is distributed from the frontend to the backend pool, specifying
protocol, port, and health probe.
- **Health Probe**: Monitors the health of backend instances to ensure traffic is only sent to healthy VMs.
- **NAT Rule**: Maps inbound traffic on a specific frontend port to a VM’s private IP and port for direct access.
- **Outbound Rule**: Controls how outbound traffic is handled, allowing backend instances to communicate externally
using the load balancer’s frontend IP.
- **Floating IP**: Enables direct traffic passthrough without SNAT, useful for high-availability scenarios.
---
## Difference Between Load Balancing Rule and NAT Rule
### **Load Balancer (LB) Rule**
- Distributes traffic across multiple backend VMs.
- Used for high availability and scalability.
- Works at Layer 4 (TCP/UDP).
- Requires a backend pool.
**Example Scenario:**
A web application is hosted on three VMs. An LB rule is created to forward traffic from Public IP:80 to Backend Pool:80.
When users visit the website, traffic is distributed across the three VMs to ensure availability.
### **NAT Rule**
- Forwards traffic from a specific frontend port to a single VM.
- Used for direct access to individual VMs.
- Works at Layer 4 (TCP/UDP).
- Does not require a backend pool.
**Example Scenario:**
A company needs SSH access to two VMs behind a load balancer. Two NAT rules are created:
- Public IP:2201 → VM1:22
- Public IP:2202 → VM2:22
Admins can connect using `ssh -p 2201 user@public-ip` to access VM1 and `ssh -p 2202 user@public-ip` for VM2.
## Terraform Modules docs
- https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/lb
- https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/lb_backend_address_pool
- https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/lb_rule
- https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/resources/lb_nat_rule