The Hub Model
When you have many VPCs and on premises networks, pairwise peering becomes an unmanageable mesh. A transit gateway acts as a central hub that each network attaches to once, so any attachment can reach any other through the hub.
Why It Scales
The hub replaces a quadratic number of links with a linear one.
- Each VPC needs only one attachment to the hub instead of links to every peer.
- The gateway holds route tables that decide which attachments can reach which.
- It supports transitive routing, so traffic can flow through the hub between any two attached networks.
Segmentation
A single transit gateway can carry multiple route tables, letting you keep groups of attachments separate. For example, production and test VPCs can attach to the same gateway yet remain isolated by associating them with different route tables. This gives both consolidation and controlled separation.
Key idea
A transit gateway is a central hub that turns a quadratic mesh of peerings into linear attachments, supports transitive routing, and uses multiple route tables to segment which networks can reach each other.