Oracle Database@AWS: DNS Configuration for Hybrid Cloud Connectivity
If you’ve spent any time setting up Oracle databases in AWS, you already know that half the battle isn’t the database itself — it’s getting the networking right. Compute and storage are the easy parts. What trips people up, consistently, is DNS.
That’s especially true with Oracle Database@AWS, where your applications live in AWS but your Oracle databases are actually running on OCI infrastructure under the hood. Cross-cloud name resolution sounds straightforward until it isn’t, and when it breaks, it looks exactly like a database problem even when the database is perfectly healthy.
This guide walks through how DNS actually works in this setup, what gets configured automatically, and what you still need to do yourself on the AWS side.
What the Oracle Database Network Actually Is
When you deploy an Oracle Database Network and peer it with your AWS VPC, you’re building a private bridge between two cloud environments. Your applications stay in AWS. Your Oracle databases sit inside OCI-managed infrastructure. DNS is what lets those two sides talk to each other using names instead of raw IP addresses.
Without clean DNS resolution, your applications can’t reliably find their database endpoints — and in environments where infrastructure changes regularly, hardcoding IPs is a maintenance nightmare waiting to happen.
Your Two DNS Options
Oracle gives you two paths depending on what you’re running.
The first is the default domain — oraclevcn.com — which Oracle manages for you. It works for both Exadata Database Service on Dedicated Infrastructure and Autonomous Database on Dedicated Exadata Infrastructure. You can add a custom prefix, but it’s capped at 15 characters. Something like client.oudbaws.oraclevcn.com.
The second option is a custom domain. This is only available for Exadata Database Service on Dedicated Infrastructure, but it gives you full control over naming. You can use up to 253 characters, which means you can fit your own enterprise naming conventions without compromise.
Most teams stick with the default domain unless they have a specific reason to use custom — usually organizational naming standards or integration with existing DNS infrastructure.
What OCI Sets Up Automatically
Here’s where Oracle earns some goodwill: when you deploy the Oracle Database Network, OCI automatically creates the DNS resolver endpoints you need on its side. You get a listener endpoint that receives incoming DNS queries from AWS, and a forwarder endpoint that handles the other direction — OCI forwarding queries back toward AWS when needed.
These two components are the actual mechanism behind cross-cloud name resolution. You don’t have to build them. They’re just there.
The catch is that AWS doesn’t reciprocate automatically. Route 53 still needs manual setup.
The AWS Side: What You Need to Configure
This is where most of the hands-on work happens. Here’s the sequence:
Security Groups first. Before anything DNS-related will work, you need to allow TCP and UDP traffic on port 53. This is the most commonly missed step, and it causes the most head-scratching when things don’t work.
Create Route 53 Resolver Endpoints. You need both an inbound and an outbound endpoint. Deploy them across multiple Availability Zones — if one AZ has issues and your DNS endpoints are in a single zone, you’ll lose database connectivity for the whole VPC.
Set up Resolver Rules. Create a forwarding rule for oraclevcn.com (or your custom domain if you went that route). This tells Route 53 which queries should be forwarded to OCI instead of resolved locally.
Associate the rule with your VPC. The rule does nothing until it’s attached to the VPC where your applications run. Easy to forget, surprisingly easy to miss in documentation.
Connect the outbound endpoint to OCI. The outbound Route 53 endpoint needs to know where to send Oracle-related DNS queries — specifically, the IP address of the OCI DNS listener endpoint, on port 53.
Once those six steps are done, the two clouds can exchange DNS queries successfully.
What Happens When Your App Connects
The full resolution flow looks like this: your application asks for a database hostname, Route 53 checks its resolver rules, matches the Oracle domain, and forwards the query through the outbound endpoint to the OCI listener. OCI’s DNS resolver looks up the database, returns the IP, and your application connects.
The whole thing takes milliseconds and is completely transparent to the application. From the app’s perspective, it just resolved a hostname. The fact that the resolution crossed cloud boundaries doesn’t matter.
Finding Your DNS Endpoints in OCI
If you want to inspect the DNS components OCI created, you can find them through the console:
Oracle Database Network → OCI Resources → Virtual Cloud Network → DNS Resolver
There you’ll see the listener and forwarder endpoints, the private DNS zones, and the associated records. OCI also creates private DNS zones that hold the actual database hostnames and their IP addresses — this is how internal service discovery works while keeping everything off the public internet.
A Few Things Worth Keeping in Mind
Port 53 is the most common culprit when DNS stops working. If connectivity suddenly breaks and the database seems fine, check your security group rules before anything else.
DNS failures and database failures look the same to an application. Build monitoring around DNS resolution specifically, not just database ping.
If your architecture involves transitive routing, make sure the relevant subnets can actually reach the OCI DNS listener endpoint. Transitive routing setups have more places where traffic can get quietly dropped.
And keep your DNS prefixes meaningful. Something like prod-east.oudbaws.oraclevcn.com is going to save you confusion six months from now when you’re troubleshooting at 2am.
The Bottom Line
Oracle Database@AWS is a genuinely capable hybrid architecture. The performance is real, and the AWS-native networking integration is well thought out. But the whole thing depends on DNS being set up correctly, because every single database connection goes through it.
OCI takes care of its side automatically. Your job is Route 53 — the resolver endpoints, the forwarding rules, and the VPC associations. Get those right, and applications talk to Oracle databases across cloud boundaries as if they were on the same network. Get them wrong, and you’ll spend a lot of time ruling out database problems that were never database problems to begin with.
