Transit Gateway/DX route propagation to VPC route tables


A customer is looking to attach DX's to multiple VPC's via Transit Gateway.

DX's are connected to Transit Gateways via DX Gateways. DXGW's can receive and propagate routes to a VPC via BGP.

Is it correct to say:

  1. DXGW and TXGW can exchange routes advertised to DXGW from on-prem to the TXGW route table
  2. Since TXGW can't propagate routes to the VPC routing table, one loses the ability to propagate on-prem routes to the VPC routing table via BGP, therefore requiring statics?

Looking for guidance on how route propagation flows through the stack.

1 Answer
Accepted Answer
  1. Yes, #1 and #2 are correct. TGW route table(hub) will receive the BGP advertisements from transit-vif, however, TGW will not propagate routes to individual VPC routing table (spoke).
  2. As a best practice, once the routing domain management is shifted to TGW (hub and spoke), do the routing management entirely in TGW than to do maintain them in two separate routing tables for DX, VPN cases.
  3. The technical reason behind is that TGW doesn't have tight routing entries limitation to the route table as compared to that of a VPC routing table that is associated with the individual ENIs.
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