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I'm testing some cloudformation infrastructure templates, and I noticed that most of the examples include routing tables to connect private subnets to public subnets, but my question then is:

if two private subnets exist in different AZs (and are attached to individual routing tables) and the resources within them may need to access a resource on the other subnet (for example a private service on the subnet 1 accessing a database on the subnet 2)

  1. Should I create a route to connect the two private subnets in each of their routing tables?
  2. Would it be a better practice to attach both subnets to a single shared routing table (both CIDRs are contiguous)?
  • Both subnets are on the same VPC – Manatax Aug 9 at 21:16
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Are they in the same VPC? If yes it should just work as the VPC CIDR route will take care of all the subnets intercommunication.

  • yes, they are on the same VPC, but if that is the case, then why do I need to connect private a public subnets? take into account I'm not using the default routing table. All subnets currently have their own routing table. – Manatax Aug 9 at 21:15
  • I see, I'm not connecting the private to the public, but the private to the NAT in the public... – Manatax Aug 9 at 21:36

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