ICMP - Internet Control Message Protocol

https://stackoverflow.com/questions/21981796/cannot-ping-aws-ec2-instance

Add a new EC2 security group inbound rule:

• Type: Custom ICMP rule
• Protocol: Echo Request
• Port: N/A
• Source: your choice (I would select Anywhere to be able to ping from any machine)

The related ping utility is implemented using the ICMP echo request and echo reply messages. 

 

https://en.wikipedia.org/wiki/Internet_Control_Message_Protocol

Function: Send ICMP ECHO_REQUEST to network hosts

Syntax: ping [-aAbBdDfhLnOqrRUvV6] [-c count] [-F...