title: <AWS VPC> Unable to ping private subnet instance from a public subnet instance
body: <p>May I seek for assistance about a lab exercise on AWS VPC that I was going through? Thanks.</p>
  
  <p>I created a new VPC, a public and private subnet respectively, and then launched 2 EC2 instances into each of the subnet respectively. I also setup the security groups required for pinging (ICMP) access on the private subnet security group. However, I could not ping the instance in the private subnet from the instance in the public subnet.</p>
  
  <p>Below are the setup:</p>
  
  <p>VPC: (CIDR block 10.0.0.0/16)</p>
  
  <p><a href="https://i.stack.imgur.com/sAEou.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/sAEou.png" alt="enter image description here"></a></p>
  
  <p>Public subnet: (CIDR block 10.0.1.0/24)</p>
  
  <p><a href="https://i.stack.imgur.com/RPgxy.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RPgxy.png" alt="enter image description here"></a></p>
  
  <p>Private subnet: (CIDR block 10.0.2.0/24)</p>
  
  <p><a href="https://i.stack.imgur.com/s8CZS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/s8CZS.png" alt="enter image description here"></a></p>
  
  <p>Route table for public subnet:</p>
  
  <p><a href="https://i.stack.imgur.com/AqB6x.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AqB6x.png" alt="enter image description here"></a></p>
  
  <p>Route table for private subnet:</p>
  
  <p><a href="https://i.stack.imgur.com/f3rpd.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/f3rpd.png" alt="enter image description here"></a></p>
  
  <p>Security group for public facing instance:</p>
  
  <p><a href="https://i.stack.imgur.com/o4tGE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/o4tGE.png" alt="enter image description here"></a></p>
  
  <p>Security group for private facing instance: (All ICMP - IPv4 allowed from private subnet CIDR block)</p>
  
  <p><a href="https://i.stack.imgur.com/IA3tp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/IA3tp.png" alt="enter image description here"></a></p>
  
  <p>Public facing EC2 instance launched in public subnet:</p>
  
  <p><a href="https://i.stack.imgur.com/F9mGm.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/F9mGm.png" alt="enter image description here"></a></p>
  
  <p>Private facing EC2 instance launched in private subnet:</p>
  
  <p><a href="https://i.stack.imgur.com/rmJJP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/rmJJP.png" alt="enter image description here"></a></p>
  
  <p>SSH-ed into public instance, but then cannot ping private instance from there:</p>
  
  <p><a href="https://i.stack.imgur.com/M5A3P.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/M5A3P.png" alt="enter image description here"></a></p>
  
  <p>Additionally, tried to SSH into the private instance from the public instance (private key already added to public instance), also failed:</p>
  
  <p><a href="https://i.stack.imgur.com/uqXBv.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/uqXBv.png" alt="enter image description here"></a></p>
  
  <p>Thank you very for your help in advance.</p>