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Sam-T
Sam-T

Reputation: 1965

AWS VPC Peering

In a 3-way peering connection A to B and A to C. Can A address same instance IP/32 in both B and C via peering connection - I am not sure. Both B and C have matching /16 CIDRs.

Routing for Response Traffic - simply talks about A sending responses back to correct calling instance(in B).

enter image description here VPC Peering

But does not talk about instance in C calling A, neither A calling B or C. What will happen when same /32 from C calls A.

Upvotes: 1

Views: 937

Answers (1)

John Hanley
John Hanley

Reputation: 81336

Form the drawing in the reference link that you provided the route table looks like this:

Destination Target
172.16.0.0/16   Local
10.0.1.0/24 pcx-aaaabbbb
10.0.0.0/24 pcx-aaaacccc

Therefore if Subnet A sends a packet in to an IP address in Subnet B (10.0.1.0/24), it will go to VPC B. Since the two Subnet Bs have overlapping CIDRs the route table will determine the destination. PCX-AAAABBBB has an entry for 10.0.1.0/24.

Instances in VPC C Subnet B will not be able to talk to VPC A as there is no return route back to VPC C. The response for those packets will either be dropped or sent to VPC B Subnet B.

Upvotes: 1

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