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VPC

VPC & Subnets Primer

  • VPC -Virtual Private Cloud: private network to deploy your resources (regional resource)
  • Subnets allow you to partition your network inside your VPC (Availability Zone resource)
  • A public subnet is a subnet that is accessible from the internet
  • A private subnet is a subnet that is not accessible from the internet
  • To define access to the internet and between subnets, we use Route Tables.

Internet Gateway & NAT Gateways

  • Internet Gateways helps our VPC instances connect with the internet
  • Public Subnets have a route to the internet gateway.
  • NAT Gateways (AWS-managed) & NAT Instances (self-managed) allow your instances in your Private Subnets to access the internet while remaining private

Network ACL & Security Groups

  • NACL (Network ACL)
    • A firewall which controls traffic from and to subnet
    • Can have ALLOW and DENY rules
    • Are attached at the Subnet level
    • Rules only include IP addresses
  • Security Groups
    • A firewall that controls traffic to and from an ENI / an EC2 Instance
    • Can have only ALLOW rules
    • Rules include IP addresses and other security groups

Network ACLs vs Security Groups

Security Group Network ACL
Operates at the instance level Operates at the subnet level
Supports allow rules only Supports allow rules and deny rules
Is stateful: Return traffic is automatically allowed, regardless of any rules Is stateless: Return traffic must be explicitly allowed by rules
We evaluate all rules before deciding whether to allow traffic We process rules in number order when deciding whether to allow traffic
Applies to an instance only if someone specifies the security group when launching the instance, or associates the security group with the instance later on Automatically applies to all instances in the subnets it's associated with (therefore, you don't have to rely on users to specify the security group)

https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Security.html

VPC Flow Logs

  • Capture information about IP traffic going into your interfaces:
    • VPC Flow Logs
    • Subnet Flow Logs
    • Elastic Network Interface Flow Logs
  • Helps to monitor & troubleshoot connectivity issues. Example:
    • Subnets to internet
    • Subnets to subnets
    • Internet to subnets
  • Captures network information from AWS managed interfaces too: Elastic Load Balancers, ElastiCache, RDS, Aurora, etc…
  • VPC Flow logs data can go to S3 / CloudWatch Logs

VPC Peering

  • Connect two VPC, privately using AWS’ network
  • Make them behave as if they were in the same network
  • Must not have overlapping CIDR (IP address range)
  • VPC Peering connection is not transitive (must be established for each VPC that need to communicate with one another)

VPC Endpoints

  • Endpoints allow you to connect to AWS Services using a private network instead of the public www network
  • This gives you enhanced security and lower latency to access AWS services
  • VPC Endpoint Gateway: S3 & DynamoDB
  • VPC Endpoint Interface: the rest

Site to Site VPN & Direct Connect

  • Site to Site VPN
    • Connect an on-premises VPN to AWS
    • The connection is automatically encrypted
    • Goes over the public internet
    • On-premises: must use a Customer Gateway (CGW)
    • AWS: must use a Virtual Private Gateway (VGW)
  • Direct Connect (DX)
    • Establish a physical connection between on-premises and AWS
    • The connection is private, secure and fast
    • Goes over a private network
    • Takes at least a month to establish

Transit Gateway

  • For having transitive peering between thousands of VPC and on-premises, hub-and-spoke (star) connection
  • One single Gateway to provide this functionality
  • Works with Direct Connect Gateway, VPN connections

VPC Summary

  • VPC: Virtual Private Cloud
  • Subnets:Tied to an AZ, network partition of the VPC
  • Internet Gateway: at the VPC level, provide Internet Access
  • NAT Gateway / Instances: give internet access to private subnets
  • NACL: Stateless, subnet rules for inbound and outbound
  • Security Groups: Stateful, operate at the EC2 instance level or ENI
  • VPC Peering: Connect two VPC with non overlapping IP ranges, nontransitive
  • VPC Endpoints: Provide private access to AWS Services within VPC
  • VPC Flow Logs: network traffic logs
  • Site to Site VPN: VPN over public internet between on-premises DC and AWS
  • Direct Connect: direct private connection to AWS
  • Transit Gateway: Connect thousands of VPC and on-premises networks together

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