Hey everyone! I'm struggling to set up VPC peering between two virtual private clouds (VPCs). Here's my setup: I've got **VPC A** which contains an application with RDS and EC2 instances, and **VPC B** that houses only EC2 instances. I need the EC2s in **VPC B** to connect to the RDS in **VPC A**.
I've created route tables for both the subnets in **VPC A** (where the RDS is) and **VPC B** (with the EC2 instances), and both are referencing the VPC peering connection. I can successfully ping and SSH between the EC2s in both VPCs, so the peering itself seems to work. However, I'm unable to connect to the RDS. I've allowed inbound access on the RDS security group for the VPC CIDR range (10.0.0.0/16), but the RDS connection still fails. Any suggestions on what I might be overlooking?
4 Answers
This kind of connectivity issue often boils down to a few common things. Start by looking at VPC flow logs; they can help you debug the connectivity problems, showing you where the traffic might be getting blocked.
Everything you’ve mentioned looks solid, but sometimes what's on paper doesn't translate to reality. Double-check your application of those settings; it’s easy to miss a minor detail. Also, AWS has a reachability analyzer which can help you test your connectivity and identify issues.
Definitely check the security group settings for your RDS. It needs to have rules that allow access from the CIDR of the other VPC. If it's not correctly set, that could be the reason for your connection issues.
Since your EC2-to-EC2 communication works, it sounds like the peering setup is correct. I'd recommend checking the route tables again to ensure that the subnets where your RDS is located are correctly associated with the route table used by the EC2 instances. Also, make sure that the security group for the RDS allows connections from the other VPC's CIDR.
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