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Network Security Group At The Subnet Level In Azure

In this article, we will add a network security group at the subnet level.

Purpose

Applying the NSG at the subnet level filters the traffic at the subnet level before it goes to the virtual machines. The following table explains the impact of NSG at the subnet level.

	NSG at the subnet level	NSG at network	Impact
Traffic through port 80	Denied	Not applicable	Traffic is denied at the subnet level
Traffic through port 80	Allowed	Denied	No traffic from port 80
Traffic through port 80	Allowed	Allowed	Traffic is allowed from port 80

Let us work on the implementation part.

Creation Of The Virtual Machine

The first step is to create the virtual machine. For this example, I have created a virtual machine "myVM" in the "North Europe" region.

Picture showing the virtual machine in the Azure portal

Click to Enlarge

Creating A Network Security Group

For creating a network security group, search the word "network" in the search box. Click on the "Network security groups" service in the search result.

Picture showing the network security groups in the Azure portal

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A screen will appear to add the network security group. Click on the "+ Add" button.

Picture showing the Add button for adding the new network security group

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In the “Create network security group” screen, enter the "Name" and select the "Region" of the network security group. Click on the "Review + Create" button for the validation of input data.

Once the validation is completed, click on the "Create" button to create the network security group.

Note → The region of the virtual network in which the virtual machine is created and the network security group should be the same.

Picture showing the Create new network security group screen for creating the network security group

Click to Enlarge

Add NSG At The Subnet Level

To add the NSG at the subnet level, click on the "Subnets" submenu in the network security group. Click on the "+ Associate" button.

Picture showing the Associate button for associating network security group at the subnet level

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A docked window will appear on the right-hand side. Select the virtual network and the subnet and then click on the "OK" button.

Picture Showing the Associate subnet screen for associating subnet with the network security group

Click to Enlarge

Check The NSG Rules In The Virtual Machine

In the virtual machine, go to the Networking submenu. There you can see the NSG at the network interface as well as the subnet level.

Picture Showing the network security group rules at the subnet and network interface levels

Click to Enlarge

Posted By -	Karan Gupta

Posted On -	Friday, May 21, 2021

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