How can I whitelist connections from my Lightsail Container Instance to my MsSQL RDS database

Question

I have both a Ubuntu based Instance/VM as well as a Ubuntu based container service running in Lightsail currently. Additionally I have a MsSQL RDS instance running in AWS in the same region in the regions default VPC.

I managed to successfully activate VPC peering in my Lightsail account. Additionally I have whitelisted connections from any Lightsail services by allowing connections from the full 172.26.0.0/16 IP range that Lightsail services use. This has allowed me to connect from my regular Instance/VM without issues. However from my Lighstail Container Service attempts to connect to the database timeout.

How can I get this working?

• Dovid Gefen: I now also whitelisted Lightsails IPv6 IP range 2600:1f18:10ff:4c00::/56 as well just in case its connecting via IPv6 and this did not help as well

Answer 1

Make sure to verify that the routes are correctly set up in the subnet where your RDS instance is located. To do this: • Go to the VPC settings in your AWS Console. • Navigate to Subnets and select the subnet where your RDS instance is located. • Click on Route Tables.

There should be a route similar to this: • Destination: 172.26.0.0/16 • Target: pcx-******** (your VPC peering connection).

For some reason, when a peering connection is created, it doesn’t automatically add routes for subnets associated with an Internet Gateway (if that’s your case). You’ll need to manually add the route to enable communication.

• Dovid Gefen: Thanks, with your help I figured out that contrary to what I thought the RDS instance was not connected to the regions default VPC. Once I switched the RDS database to the correct VPC everything started working correctly

Answer 2

It turns out that my RDS MsSQL was not in the region's default VPC like I thought. Once I moved the instance to the correct VPC everything started working properly.