NSG rules (inbound, outbound) in Azure - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an NSG in Azure?

An NSG (Network Security Group) is like a security guard for your cloud network. It controls which traffic can come in (inbound) and go out (outbound) of your virtual machines or subnets.

beginner

What does an inbound NSG rule do?

An inbound NSG rule controls the traffic coming into your resource. It decides if incoming data is allowed or blocked based on rules like IP address, port, and protocol.

beginner

What does an outbound NSG rule do?

An outbound NSG rule controls the traffic leaving your resource. It decides if outgoing data is allowed or blocked based on rules like destination IP, port, and protocol.

intermediate

What are the key parts of an NSG rule?

Each NSG rule has: a priority number (which rule runs first), direction (inbound or outbound), source and destination (IP or subnet), protocol (TCP, UDP, or Any), port range, and action (allow or deny).

intermediate

Why is rule priority important in NSG?

Rule priority decides which rule applies first. Lower numbers have higher priority. If a higher priority rule allows or denies traffic, later rules are ignored for that traffic.

What does an inbound NSG rule control?

A Traffic inside a virtual machine

B Traffic leaving a resource

C Traffic between two Azure regions

D Traffic coming into a resource

Inbound NSG rules control incoming traffic to your resource.

Which part of an NSG rule decides the order of evaluation?

A Source IP

B Priority number

C Protocol type

D Port range

Priority number determines which rule is checked first.

What action can an NSG rule take on traffic?

A Allow or Deny

B Encrypt or Decrypt

C Route or Block

D Log or Ignore

NSG rules either allow or deny traffic based on conditions.

Which protocol can you specify in an NSG rule?

A HTTP only

B FTP only

C TCP, UDP, or Any

D SMTP only

NSG rules support TCP, UDP, or Any protocol.

If two NSG rules conflict, which one applies?

A The one with lower priority number

B The one created last

C The one with higher priority number

D Both apply equally

The rule with the lower priority number (higher priority) applies first.

Explain how inbound and outbound NSG rules work together to protect an Azure resource.

Think of inbound as the front door and outbound as the back door security.

Describe the key components you need to set when creating an NSG rule.

Imagine setting rules for who can enter or leave your house and how.

Practice

1. What is the primary purpose of an Azure Network Security Group (NSG)?

easy

A. To store data securely in the cloud

B. To manage user identities and access

C. To control inbound and outbound network traffic to resources

D. To monitor application performance

Solution

1. Step 1: Understand NSG function

   NSGs are designed to filter network traffic to and from Azure resources.

2. Step 2: Compare options

   Only To control inbound and outbound network traffic to resources describes controlling inbound and outbound traffic, which matches NSG's role.

3. Final Answer:

   To control inbound and outbound network traffic to resources -> Option C

4. Quick Check:

   NSG controls traffic = B [OK]

Hint: NSG controls traffic flow, not data or users [OK]

Common Mistakes:

• Confusing NSG with storage or identity services
• Thinking NSG monitors performance
• Assuming NSG manages user access

2. Which of the following is the correct way to specify an inbound NSG rule to allow TCP traffic on port 80?

easy

A. Priority: 100, Direction: Inbound, Protocol: TCP, Port: 80, Action: Allow

B. Priority: 100, Direction: Inbound, Protocol: UDP, Port: 80, Action: Allow

C. Priority: 100, Direction: Outbound, Protocol: TCP, Port: 80, Action: Allow

D. Priority: 100, Direction: Inbound, Protocol: TCP, Port: 443, Action: Allow

Solution

1. Step 1: Identify direction and protocol

   The question asks for inbound TCP traffic on port 80, so Direction must be Inbound and Protocol TCP.

2. Step 2: Check port and action

   Port must be 80 and Action Allow to permit traffic.

3. Final Answer:

   Priority: 100, Direction: Inbound, Protocol: TCP, Port: 80, Action: Allow -> Option A

4. Quick Check:

   Inbound TCP port 80 allow = C [OK]

Hint: Inbound + TCP + port 80 + Allow = correct rule [OK]

Common Mistakes:

• Using outbound direction instead of inbound
• Using UDP protocol instead of TCP
• Specifying wrong port number

3. Given these NSG rules applied in order of priority:
1) Priority 100: Allow inbound TCP port 22 from 10.0.0.0/24
2) Priority 200: Deny inbound TCP port 22 from any
What will happen if a connection attempt comes from IP 10.0.0.5 on port 22?

medium

A. The connection is allowed because allow rule has higher priority

B. The connection is allowed because deny rules do not apply to private IPs

C. The connection is denied because default deny applies

D. The connection is denied because deny rule has higher priority

Solution

1. Step 1: Understand rule priority

   Lower priority number means higher priority. Priority 100 rule is evaluated before 200.

2. Step 2: Evaluate matching rules

   IP 10.0.0.5 matches allow rule at priority 100, so connection is allowed before deny rule is checked.

3. Final Answer:

   The connection is allowed because allow rule has higher priority -> Option A

4. Quick Check:

   Lower priority allow beats higher priority deny = D [OK]

Hint: Lower priority number rules apply first [OK]

Common Mistakes:

• Assuming deny always overrides allow
• Ignoring rule priority order
• Thinking private IPs bypass deny rules

4. You created an NSG rule to allow outbound HTTPS traffic on port 443, but traffic is still blocked. Which of the following is the most likely cause?

medium

A. The source IP address range is set to 0.0.0.0/0

B. The NSG rule is set to inbound instead of outbound

C. The protocol is set to UDP instead of TCP

D. There is a higher priority outbound deny rule blocking port 443

Solution

1. Step 1: Check rule priority and direction

   If traffic is blocked despite allow rule, a deny rule with higher priority likely blocks it.

2. Step 2: Evaluate other options

   Inbound vs outbound mismatch or protocol mismatch would cause no effect, but the question states rule exists for outbound HTTPS.

3. Final Answer:

   There is a higher priority outbound deny rule blocking port 443 -> Option D

4. Quick Check:

   Higher priority deny blocks traffic despite allow = A [OK]

Hint: Check for higher priority deny rules first [OK]

Common Mistakes:

• Ignoring rule priority order
• Confusing inbound and outbound directions
• Assuming source IP 0.0.0.0/0 blocks traffic

5. You want to allow inbound HTTP traffic only from a specific IP range 192.168.1.0/24 and deny all other inbound HTTP traffic. Which NSG rule configuration achieves this?

hard

A. Priority 100: Deny inbound TCP port 80 from any; Priority 200: Allow inbound TCP port 80 from 192.168.1.0/24

B. Priority 100: Allow inbound TCP port 80 from 192.168.1.0/24; Priority 200: Deny inbound TCP port 80 from any

C. Priority 100: Allow inbound TCP port 80 from any; Priority 200: Deny inbound TCP port 80 from 192.168.1.0/24

D. Priority 100: Deny inbound TCP port 80 from 192.168.1.0/24; Priority 200: Allow inbound TCP port 80 from any

Solution

1. Step 1: Allow specific IP range first

   Allow rule with higher priority (lower number) must permit traffic from 192.168.1.0/24.

2. Step 2: Deny all other IPs

   Deny rule with lower priority blocks all other inbound HTTP traffic.

3. Final Answer:

   Priority 100: Allow inbound TCP port 80 from 192.168.1.0/24; Priority 200: Deny inbound TCP port 80 from any -> Option B

4. Quick Check:

   Allow specific IP first, then deny others = A [OK]

Hint: Allow specific IP with lower priority number, deny others after [OK]

Common Mistakes:

• Placing deny rule before allow rule
• Allowing all IPs instead of specific range
• Using wrong priority numbers