Connecting to EC2 instances in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

How does SSH key pair affect EC2 instance connection?

You launched an EC2 instance with a specific SSH key pair. What happens if you try to connect to the instance using a different private key?

A The connection succeeds but you get a warning about mismatched keys.

B The connection is refused because the private key does not match the instance's public key.

C The connection succeeds without any issues.

D The instance automatically updates to accept the new key.

💡 Hint

Think about how SSH authentication works with key pairs.

EC2 instances use the public key from the key pair to allow SSH connections. If you use a private key that does not match the public key on the instance, the connection is refused.

❓ Architecture

intermediate

Which security group rule allows SSH access to an EC2 instance from anywhere?

You want to connect to your EC2 instance via SSH from any location. Which inbound security group rule should you configure?

A Allow inbound TCP traffic on port 80 from 0.0.0.0/0

B Allow inbound UDP traffic on port 22 from 0.0.0.0/0

C Allow inbound TCP traffic on port 22 from 0.0.0.0/0

D Allow inbound TCP traffic on port 22 from the instance's private IP

💡 Hint

SSH uses a specific port and protocol.

SSH uses TCP port 22. Allowing inbound TCP traffic on port 22 from 0.0.0.0/0 means any IP can attempt to connect via SSH.

❓ Configuration

advanced

What is the effect of disabling source/destination check on an EC2 instance?

You disable the source/destination check on an EC2 instance. What behavior does this enable?

A The instance will automatically update its security group.

B The instance will reject all incoming traffic.

C The instance will only accept traffic from its own IP address.

D The instance can act as a network router or NAT device.

💡 Hint

Think about routing and forwarding network packets.

Disabling source/destination check allows the instance to forward traffic that is not specifically addressed to it, enabling it to act as a router or NAT.

❓ security

advanced

What happens if you expose your EC2 private key file publicly?

You accidentally upload your EC2 private key file to a public repository. What is the immediate risk?

A Anyone with the key can connect to your EC2 instances using SSH.

B AWS automatically revokes the key and blocks access.

C The key becomes invalid after 24 hours automatically.

D Only users in your AWS account can use the key.

💡 Hint

Consider what the private key controls in SSH access.

The private key is the secret that allows SSH access. If exposed publicly, anyone can use it to connect to your EC2 instances that accept that key.

🧠 Conceptual

expert

Why might you use Session Manager instead of SSH to connect to EC2 instances?

Session Manager is an AWS Systems Manager feature. What is a key advantage of using Session Manager over traditional SSH to connect to EC2 instances?

A It allows secure shell access without opening inbound ports or managing SSH keys.

B It requires you to open port 22 but uses a different authentication method.

C It only works with Windows instances, not Linux.

D It requires a VPN connection to your VPC.

💡 Hint

Think about network security and key management.

Session Manager lets you connect securely without opening SSH ports or handling private keys, reducing attack surface and simplifying access.