Inbound and outbound rules in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

Understanding Security Group Inbound Rules

You have a security group with the following inbound rule:

Type: SSH
Protocol: TCP
Port Range: 22
Source: 0.0.0.0/0

What is the effect of this rule?

A Blocks SSH access from all IP addresses to instances associated with this security group.

B Allows SSH access only from within the same VPC.

C Allows SSH access only from a specific IP address.

D Allows SSH access from any IP address to instances associated with this security group.

💡 Hint

Think about what 0.0.0.0/0 means in networking.

The source 0.0.0.0/0 means any IP address. So this rule allows SSH (port 22) from anywhere.

❓ Architecture

intermediate

Outbound Rules for Internet Access

You want your EC2 instances in a private subnet to access the internet for software updates. Which outbound rule should you add to the security group?

A Allow all outbound traffic (All protocols, All ports, Destination 0.0.0.0/0).

B Allow inbound HTTP traffic from 0.0.0.0/0.

C Allow inbound traffic on port 80 from the internet.

D Allow outbound traffic only on port 22 to 0.0.0.0/0.

💡 Hint

Think about what outbound rules control and what is needed for internet access.

Outbound rules control traffic leaving the instance. Allowing all outbound traffic lets instances reach the internet for updates.

❓ security

advanced

Restricting Inbound Access to a Specific IP

You want to allow HTTP access (port 80) only from your office IP 203.0.113.5. Which inbound rule configuration is correct?

A Type: HTTP, Protocol: TCP, Port Range: 80, Source: 203.0.113.5/32

B Type: HTTP, Protocol: TCP, Port Range: 80, Source: 0.0.0.0/0

C Type: HTTP, Protocol: TCP, Port Range: 80, Source: 203.0.113.0/24

D Type: HTTP, Protocol: UDP, Port Range: 80, Source: 203.0.113.5/32

💡 Hint

Consider the CIDR notation for a single IP and the correct protocol for HTTP.

203.0.113.5/32 means only that single IP. HTTP uses TCP protocol on port 80.

✅ Best Practice

advanced

Best Practice for Outbound Rules in Security Groups

Which of the following is the best practice for configuring outbound rules in AWS security groups?

A Deny all outbound traffic by default and open ports as needed.

B Allow all outbound traffic by default unless there is a specific reason to restrict it.

C Allow outbound traffic only on port 22 for SSH.

D Allow outbound traffic only on port 80 for HTTP.

💡 Hint

Think about ease of management and common AWS defaults.

AWS security groups allow all outbound traffic by default. This is generally best unless you have strict security needs.

🧠 Conceptual

expert

Effect of Missing Outbound Rules

If a security group has inbound rules allowing HTTP (port 80) from anywhere but has no outbound rules configured, what will happen when an instance receives an HTTP request?

A The instance will send a response but cannot receive further requests.

B The instance will block the incoming HTTP request due to missing outbound rules.

C The instance will receive and respond to the request normally.

D The instance will receive the request but cannot send a response back, causing the connection to fail.

💡 Hint

Remember how security groups handle stateful traffic.

Security groups are stateful. Responses to allowed inbound traffic are automatically permitted outbound regardless of outbound rules. The instance will receive the request and respond normally.