Features:
- By default has 1 route (traffic controller)
- All attachments, in a hub and spoke design, use route tables for routing decisions
- Data is encrypted (like VPC peering)
- No route learning (propagation) across peering attachments
- Use unique ASNs
- Create a static route on VPC side to send traffic upstream to the attached TGW
- VPCs with overlapping CIDR blocks to a TGW, is not allowed
- Up to 50 peering attachments per TGW in different Regions / Accounts
Association – a route table is associated with an attachment.
Attachment – can be associated with 1 route table, and when associated, the Transit Gateway uses the route table to route traffic leaving (outgoing) that attachment. Route table associations are used when data is exiting an attachment.
Propagation – is the configuration that controls which route tables will be populated with routes known by the attachments. For isolated networks, separate the route tables and the propagations.
