
AWS Certified Advanced Networking – Specialty (ANS-C01) Certification Guide
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Of all the hybrid cloud networking options, the combination of TGW and DX gateways tends to be one of the most confusing. There are a lot of caveats for both TGW and DX gateways, and when they are combined, there are even more. The biggest ones have been covered in their respective sections, so in this section, the focus will be on common design patterns and things to consider when planning to interoperate them.
When designing TGW and DX gateway integrations, the most important thing to remember is that TGW does not advertise routes to a DX gateway attachment; the DX gateway must be configured with the prefixes to advertise across DX. What’s more, the advertised CIDRs cannot overlap other TGWs attached to the same DX gateway, so if redundancy in CIDR advertisement is needed, more DX gateways (and transit VIFs) are needed as well. This is easier to show than tell because it sounds far more complex than what will be deployed: