This is a quick post to help diagnose RDS AWS Connectivity Issues – Also read (Getting Data into AWS’ RDS    and also the official AWS RDS Oracle Full doc)

Quick Oracle Client Connection Test

Use any Oracle Client (I like dbForge, free trial for 30 days)…and try to connect to the endpoint displayed in your spun up RDS instance.

Cannot Connect to the RDS endpoint?

It can be one of four possible causes:

  1. DNS Resolution is failing for the RDS Endpoint
  2. Public Acccessibility – RDS instance is not set to ‘public’ (to enable this, you have to have step 1 – dns resolution enabled)
  3. Your own laptop’s public IP isn’t whitelisted in the RouteTable for the Subnet (containing the RDS Instance)
  4. There isn’t a route to the internet (make sure that the data subnet contains a route to the internet)

Open the Amazon RDS console.

rds publicly accessible
rds publicly accessible

Choose Databases from the navigation pane, and then select the DB instance –> Choose Modify –> Under Network & Security, choose Yes for Public accessibility.

Enabling DNS Resolution (at VPC Level) and DNS Hostnames

Go into your VPC Settings –> Edit –> Enable DNS Resolution

rds aws connectivity dns resolution vpc
rds aws connectivity dns resolution vpc

Route to the Internet for your RDS Instance

Should my Data Subnet (a private subnet) have a route to the internet? Yes – You do not have to have a 0.0.0.0/0 to the IgW. All you need is your private subnet to go through the NAT gateway to get to the internet

data subnet route to internet
data subnet route to internet

Summary

That’s all there is to it. If you have an up and running RDS Instance, ensure that it is publicly accessible; that your own desktop (or jumpbox) IP Address is whitelisted and that DNS Hostnames are enabled and resolution is enabled at the VPC Level.


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