VPC

Virtual Private Network

A VPC is private subsection of AWS or GCP that you control. You decide who can access the resources you put in your VPC.

All info from these notes is from a presentation by Sarah Zelechoski: An Introduction to Amazon VPC: Private Islands for Rent

New materials!

• https://www.digitalocean.com/community/tutorials/an-introduction-to-networking-terminology-interfaces-and-protocols

A VPC is like renting a private island from Amazon.

VPC

• Self-contained: You get a CIDR of your choosing
• You can customize your subnet structure, routing and security

Region

• Like the part of the earth where the island resides
• In AWS, you select a region that is in one geographical area
• There are multiple datacenters
• You can have the datacenter close to you or your customers
• A VPC lives in one region

Internet Gateway

• This is like the channel that takes you from your island to the ocean
• All communication with the internet happens through IGW
• One IGW per VPC
• Public subnets use as default gateway
• Private subnets use a NAT gateway to send traffic to the IGW

Subnets

Public Subnet

• Like the shallow water around the island
  • Instances have public IP
  • Traffic will flow directly to the IGW
  • Can interface with instances inside
  • Houses all ingress points to your VPC
  • Security is important! Minimize your footprint

DMZ

• Like the guest cabanas
• VPN appliance

Bastion Host

• Like the helipad
• An ingress point that is an alternative VPN
• Access prive instances
  • SSH for Admins
  • Tunnel for automation tools
• Needs strict security
  • Restrict ports
  • SSH user-specific keys

Elastic Load Balancer

• Like the arrival jetty where vistors come and walk onto the island
• Public interface
• Gateway to your applications and services
• Expose different ports outside vs. inside
• SSL and SSL termination
• High availability and failover

NAT

• Private Egrees
• Maps a private network to a public address
• Allows information from the private subnet to go out to the internet
• Often used to reach out for git, apt/yum

Private Subnet

• Instances only have private addresses
• Ingress is through an ELB
• Egress ithrough a NAT gateway
• You can lock it down more through:
  • Networks ACLs
  • Security Groups

Routing Tables

• Like a Concierge: showing people different places
• How traffic gets from place to place
• VPC CIDR is local by default
• You need private and public routing tables
  • Public: 0.0.0.0/0 is attached to your IGW
  • Private: 0.0.0.0/0 is attached to your NAT Gatewat
• There is one route table associated with a subnet
• The can be many subnets with the same route table

Network ACLs

• Like a front gate
• Controls access to a subnet
• Default allows all users

Security Groups

• Like a door lock
• Instance based (like each instance is a door)
• Associated with a network interface
• Ingress and egress
  • tcp, udp, icmp ports
  • SG or specific CIDR
• Stateful
• Principle of least privilege
• Port-based or role-based

Advanced Topics