Public and Private Subnets

• Public Subnet is associated with a route table which has route to internet gateway
• Private subnet is associated with a route table which has no route to internet gateway
• subnets will using
  • default route table, if there is no explicit connection
    
• Lets create a vpc with 3 subnets
  • public subnet
  • private subnet
  • default (route to default route table)
    
    
    
• Now lets create a internet gateway and associate that with vpc
  
• Create a route table with route to internet gateway (public rt)
  
  
• Create a route table without route to internet gateway (private rt)
  
• Lets create an ec2 instance in public subnet (we have not associated public subnet to public route table yet)
  
• Now lets try ssh connectivity using public ip
  
• Lets associate public subnet to public rt
  
  
  
  
• Lets try to reconnect
  
• Now lets try to connect to internet from public ec2
  
• Lets try to create one ec2 instance in private subnet which is explicitly connected to private route table
  
  
• Now try connecting to private route table instance using public ip
  
  
• For all the internal communications in vpc use private ips not public ip.
• Lets try to connect to internet from private ec2
  
• Private subnets cannot be connected from/to internet