What are the possible root causes of this issue?
(Choose two.)
The ELB is not configured with a proper health check.
The route tables in the VPC are configured incorrectly.
The EC2 instances are not associated with an Elastic IP address.
The security group attached to the NAT gateway is configured incorrectly.
The outbound rules on the security group attached to the EC2 instances are configured incorrectly.
Explanations:
The ELB’s health check configuration primarily affects the ability to route traffic to the EC2 instances. It does not impact outbound internet access for software updates from the EC2 instances.
If the route tables in the VPC are configured incorrectly, the EC2 instances may not have a proper route to the NAT gateway for outbound internet traffic, preventing them from accessing the internet for updates.
EC2 instances in a private subnet typically do not need Elastic IP addresses for outbound internet access when using a NAT gateway. The NAT gateway itself can have an Elastic IP, but the instances do not require it.
NAT gateways do not use security groups; they use network ACLs. Therefore, if there are issues with the NAT gateway’s configuration, they would not be due to security group settings.
If the outbound rules on the security group attached to the EC2 instances are configured incorrectly, it can block outbound traffic, preventing the instances from accessing the internet for software updates.
I strategize that the answer is:
The route tables in the VPC are configured incorrectly.