CODEWITHSUNDEEP
azureazure-virtual-machineazure-load-balancernetwork-security-groupsinbound-security-rule
Shan
Shan

Reputation: 27

Issue with Azure Standard Load Balancer not routing traffic to VM despite pre-defined inbound rule

I'm encountering an issue with Azure Load Balancer where I'm unable to access my Private VM despite having a pre-defined inbound rule that should allow traffic from the load balancer.

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Here's the setup:

Operating system: Windows (Windows Server 2022 Datacenter Azure Edition) Size: Standard B4ms (4 vcpus, 16 GiB memory) Region: East US

I have deployed a Private VM with IIS installed. I created a public Standard Load Balancer and attached the VM as a backend target. Azure automatically created an inbound rule named "AllowAzureLoadBalancerInBound" with the properties: Priority: 65001, Port: Any, Protocol: Any, Source: AzureLoadBalancer, Destination: Any, Action: Allow to the inbound rules of VM.

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Here are some additional details:

Here is my load balancing rule enter image description here

I don't have any Inbound NAT rules and Outbound rules defined.

Health probe and backend pool configurations are correct, with a 100% health probe result. enter image description here

There are no firewall issues, as explicitly adding an inbound rule for HTTP traffic allows access to the IIS page.

I'm confused about why I need to create an additional inbound rule when there's already a pre-defined rule by Azure to allow traffic from the load balancer to the backend VMs.

Any insights or suggestions on what might be causing this issue would be greatly appreciated. Thank you!

Upvotes: 0

Views: 862

Answers (1)

Venkat V
Venkat V

Reputation: 7614

Issue with Azure Standard Load Balancer not routing traffic to VM despite pre-defined inbound rule.

The issue you encountered may be due to the absence of a rule in the Network Security Group allowing traffic on port 80 from your IIS server, which is installed on the Windows Server.

IIS Server configuration

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Load balancing rule:

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Load Balancer IP:

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NSG Rule:

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The one you are referring to is not your load balancer; it is provided by default in Azure for managing Azure infrastructure. You can check the Microsoft documentation for available service tags, including AzureLoadBalancer: Available service tags: AzureLoadBalancer.

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You may refer to the Create a public load balancer to load balance VMs using the Azure portal MS Doc, as it requires opening ports that are used in load balancing rule backend ports.

For example, if you are using port 80 for the backend in the load balancer rule, you should allow it in the network security group.

The application is accessible via the Load Balancer public IP address using port 50000.

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Upvotes: 0

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