What is one reason for the issue?
The instance does not have an Elastic IP address
The instance has a security group that does not allow Internet Control Message Protocol (ICMP) traffic
The instance is not set up in a VPC using AWS Direct Connect
The instance is running in a peered VPC
Explanations:
An Elastic IP address is not required to ping the instance. The issue is related to security settings, not the IP addressing.
Security groups in AWS act as virtual firewalls. By default, security groups do not allow ICMP (ping) traffic, which causes the timeout.
AWS Direct Connect is not relevant to the ability to ping an EC2 instance. The issue is related to security group configuration.
Running in a peered VPC does not inherently cause issues with pinging. The security group settings or routing may be the issue, not the VPC configuration.
In my experience, the answer is:
The instance has a security group that does not allow Internet Control Message Protocol (ICMP) traffic