Reasons for Inaccessibility of Web Application after EC2 Server Restart
Question
You currently manage a set of web servers hosted on EC2 Servers with public IP addresses.
These IP addresses are mapped to domain names.
There was an urgent maintenance activity that had to be carried out on the servers and the servers had to be restarted.
Now the web application hosted on these EC2 Instances is not accessible via the domain names configured earlier.
Which of the following could be a reason for this.
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.Answer - D.
By default the public IP address of an EC2 Instance is released after the instance is stopped and started.
Hence the earlier IP address which were mapped to the domain names would have become invalid now.
For more information on public IP addressing, please visit the below URL:
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-instance-addressing.html#concepts-public-addressesWhen an EC2 instance is stopped and started, it can result in the public IP address of the instance being changed. The public IP address is associated with the network interface of the instance, and when the instance is stopped, the network interface is disassociated from the public IP address. When the instance is started again, a new network interface is created, and a new public IP address is associated with it.
In the scenario described, the web servers were restarted, which means that the underlying EC2 instances were stopped and started again. This could have resulted in the public IP addresses of the instances being changed. As a result, the domain names that were previously mapped to the old public IP addresses would no longer be accessible.
Option D, "The public IP addresses have changed after the instance was stopped and started," is the correct answer in this scenario.
Option A, "The Route53 hosted zone needs to be restarted," is not relevant to this scenario. Route53 is a DNS service that can be used to map domain names to IP addresses, but it does not control the allocation of public IP addresses to EC2 instances.
Option B, "The network interfaces need to initialized again," is also not relevant. The network interfaces of the EC2 instances are initialized automatically when the instances are started, and there is no manual intervention required.
Option C, "The public IP addresses need to associated to the ENI again," is partially correct. It is true that the public IP addresses are associated with the network interfaces of the instances. However, in this scenario, the issue is not that the public IP addresses need to be associated again, but rather that they may have changed during the stop/start process.
