EC2 instances cannot ping each other

Question

I have 2 EC2 Ubuntu instances. They are sharing same VPC, su.net and Security Group. Instances' firewall was turnoff. But I still can't ping each other by private IP. How to allow those instances ping each other?

Answer 1

In the security group, add "Custom ICMP" rule for "Echo Request" -- or -- "All ICMP Traffic" -- and as the source IP, instead of an address or block, add the security group's identifier, sg-xxxxxxxx.

Simply being in the same security group doesn't mean the instances can communicate among themselves. It only means they follow the same set of rules... but security group membership is a source attribute as well, on traffic originating from instances that are members of the group.

Hence, the above.

Answer 2

if it is windows instance, then you need to enable rule in firewall. And also need to add inbound rule for your private CIDR range atleast