Network Error: Connection Timed Out - Troubleshooting Guide | Exam ANS-C01

Answer - A and B.

The AWS documentation mentions the following for troubleshooting EC2 Instance connectivity.

1

Check your security group rules.

You need a security group rule that allows inbound traffic from your public IPv4 address on the proper port.

2

Check the route table for the subnet.

You need a route that sends all traffic destined outside the VPC to the internet gateway for the VPC.For more information on troubleshooting EC2 Instances please see the below link:

http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/TroubleshootingInstancesConnecting.html

When you receive an error message indicating a connection timeout, it means that your instance is not reachable from the internet. To diagnose the issue, you need to check the following:

A. Check the Inbound Security Group Rules: Security groups act as a virtual firewall that controls inbound and outbound traffic to instances. Inbound traffic is traffic that is sent to your instance from the internet. If the inbound security group rules are not configured correctly, your instance will not be reachable from the internet. Ensure that the security group attached to your instance has the necessary inbound rules to allow traffic to your instance.

B. Check the route table for the VPC: A route table contains a set of rules called routes that are used to determine where network traffic is directed. If the route table is not configured correctly, network traffic will not be able to reach your instance. Ensure that the route table for your VPC is properly configured.

C. Check if a private IP address has been assigned to the instance: An instance must have a private IP address to communicate with other resources in the VPC, such as the internet gateway. If the instance does not have a private IP address assigned, it will not be able to communicate with the internet gateway and will not be reachable from the internet.

D. Check if the instance has been assigned a private DNS name: A private DNS name is a DNS hostname that resolves to the private IP address of the instance. If the instance does not have a private DNS name assigned, it may not be reachable from the internet. However, this is not always necessary as it depends on the specific use case.

In summary, the two valid checkpoints to diagnose a connection timeout error when trying to connect to an instance from the internet are checking the inbound security group rules and checking the route table for the VPC.