VPC IP Range

• VPC = Virtual Private Cloud
• You can have multiple VPCs in an AWS region (max. 5 per region – soft limit)
• Max. CIDR per VPC is 5, for each CIDR: • Min. size is /28 (16 IP addresses) • Max. size is /16 (65536 IP addresses)
• Because VPC is private, only the Private IPv4 ranges are allowed: • 10.0.0.0 – 10.255.255.255 (10.0.0.0/8) • 172.16.0.0 – 172.31.255.255 (172.16.0.0/12) • 192.168.0.0 – 192.168.255.255 (192.168.0.0/16)

Internet Gateway (IGW)

• Allows resources (e.g., EC2 instances) in a VPC connect to the Internet
• One VPC can only be attached to one IGW and vice visa
• Route tables must also be edited!

Bastion Hosts

• We can use a Bastion Host to SSH into our private EC2 instances

• The bastion is in the public subnet which is then connected to all other private subnets

• Security Group of the EC2 Instances must allow the Security Group of the Bastion Host, or the private IP of the Bastion host

  

NAT Instance

• Allows EC2 instances in private subnets to connect to the Internet
• Must disable EC2 setting: Source / destination Check
• Must have Elastic IP attached to it
• Route Tables must be configured to route traffic from private subnets to the NAT Instance

NAT Gateway

• NAT Gateway is resilient within a single Availability Zone