Hello Anirudh Mounasamy
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The message you see the Azure Portal indicates that the backend pool was successfully added to the Azure load balancer, but for the change to take effect, you need to upgrade all the instances of the virtual machine scale set (VMSS) that you added to the backend pool.
When you add a VMSS to a backend pool, the load balancer needs to know the IP addresses of the instances in the VMSS to route traffic to them. However, these IP addresses are not available until the VMSS instances are created or updated. When you upgrade the VMSS, new instances are created or existing ones are updated with new IP addresses, which allows the load balancer to route traffic to them.
Refer below articles, for configuring a Virtual Machine Scale Set with an existing Azure Load Balancer,
Azure PowerShell: https://learn.microsoft.com/en-us/azure/load-balancer/configure-vm-scale-set-powershell
Azure CLI: https://learn.microsoft.com/en-us/azure/load-balancer/configure-vm-scale-set-cli
Azure Portal: https://learn.microsoft.com/en-us/azure/load-balancer/configure-vm-scale-set-portal
To upgrade the VMSS and add the instances to the backend pool from Azure Portal, you can follow these steps:
- Navigate to the Azure portal and select the VMSS that you want to add to the backend pool.
- Select "Update" from the top menu and then select "Upgrade".
- Choose the appropriate upgrade policy and configure any other settings as needed.
- Review and validate the upgrade, then click "OK" to initiate the upgrade.
Once the upgrade is complete, the instances in the VMSS should have IP addresses that the load balancer can use to route traffic to them, and the backend pool should be fully functional.
Hope this helps.
If you need further help on this, tag me in a comment.
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