VPC Peering

A deep dive into VPC Peering - Practical ver.

Reference: aws docs

What is VPC Peering?

• A feature that connects two different VPCs

  • Once two VPCs are connected, a pathway for internal communication is created!

• Peering can also be configured across different accounts / different regions

  • Benefits of setting up peering connections between different regions

    • DR (Disaster Recovery) configuration becomes possible

    • You can peer multiple regions and use them

      • e.g.) Accessing a Thailand service from within the country

Working with VPC Peering

• Requester VPC & Accepter VPC

  • Although the names are requester and accepter, they do not indicate direction!

    • Direction can be configured differently based on subnet communication

• Sending VPC's CIDR Block >= Receiving VPC's CIDR Block

  • Why?

    • If the receiving VPC's CIDR Block is larger than the sending VPC's CIDR Block, communication obviously won't work!

  • Typically, the CIDR Blocks of both VPCs are set to be the same, but the receiving VPC's can be smaller

    • Being smaller is not a problem

Things you should be aware of

1. When configuring a Peering Connection, the CIDR Blocks of the two VPCs must not conflict

   • Why?

     • Since the two VPCs are being connected rather than existing separately, they cannot have conflicting CIDRs

2. Additional charges apply when traffic passes through the peering connection

   • However, it's not a significant amount!