# Network Security Group (NSG)

**Network Security Group (NSG)**
NSG can be used to filter network traffic to and from Azure resources in a virtual network. NSG contains security rules that allow or deny network traffic. NSG can be applied to Subnet and Network Interface Card (LAN CARD).


- Name
- Priority
- Source
- Destination
- Protocol
- Port
- Action

**Below Diagram shows how we connect to the Azure VM and Which level we can apply NSG.**

![image.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1639239970644/zenvqfHGr.png)

**Below Diagram is the example of 3 Tier Application**

 **WEB-NSG** : With WEB-NSG we are allowing the Users from the internet to WEB-SERVER.
Ex : Source should be (any) or (particular Ip), Destination should be WEB Server.

*Note :* With the help of this NSG we can restrict internet users to connect only to the WEB-SERVER.

 **APP-NSG** : Source should be WEB-SERVER and Destination should be APP-SERVER.

*Note* : Here only WEB-SERVER can able to connect to the APP-SERVER.

**DB-NSG**  : Source Should be APP-SERVER and Destination should be DB-SERVER.

*Note* :  Here only APP-SERVER can able to connect to the DB-SERVER.

![image.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1639237730078/e94YffUD6.png)

In this way we are applying NSG to Allow/Deny INBOUND and OUTBOUND Traffic and make our environment more secure.