Round-robin DNS

You’ve probably heard of DNS, the system that turns names like example.com into IP addresses your browser can connect to. But what if you want that name to point to more than one server? What if you want to spread traffic across them all without any fancy hardware?

That’s where you’d use round-robin DNS. It’s one of the simplest forms of load balancing out there—and while it’s not perfect, it’s easy to implement, surprisingly useful, and often overlooked.

What Is Round-Robin DNS?

Round-robin DNS is a technique where multiple IP addresses are assigned to the same domain name. Each time someone looks up that domain, the DNS server hands out a different IP from the list—cycling through them in order.

Imagine you’ve got a site, yourcoolapp.com, and three servers behind it. With DNS round robin, you add three A records to your DNS zone, all pointing to different IPs:

yourcoolapp.com → 192.0.2.1  
yourcoolapp.com → 192.0.2.2  
yourcoolapp.com → 192.0.2.3  

Each visitor asking for yourcoolapp.com might get a different IP, depending on where they are and how their DNS resolver handles the list.

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How the DNS Round Robin Technique Works

When someone visits your domain, their device reaches out to a DNS server to resolve it. If you’ve added multiple DNS A records, the resolver gets a list of IPs.

Here’s the round robin part:

Most resolvers will cycle through that list. The first user might get 192.0.2.1, the second one 192.0.2.2, and so on. When they reach the end, it starts over. Simple.

But there’s a catch: DNS itself doesn’t enforce the round-robin order. It just gives out the list. What happens next depends on the client and the resolver. Some may always use the first IP. Others might randomize the list or try them in order until one responds.

Still, it works well enough for lightweight load balancing—especially when you want to spread requests across multiple servers without setting up a full load balancer.

Can Round Robin Work with CNAME Records?

Short answer: not really, and here’s why.

The DNS round robin technique only works with A records, which map a domain to an IP address. But CNAME records work differently—they point a domain to another domain, not an IP.

And DNS doesn’t let you mix multiple CNAMEs for a single hostname. If you try to set more than one, your DNS provider will throw an error or ignore the extra entries.

So if you’re thinking, “I’ll just create multiple CNAME records to different hosts and get round robin for free”—you’re out of luck.

That said, you can point a CNAME to a domain that already uses round-robin A records under the hood. But the round robin happens at that domain, not at your CNAME layer. So unless you control that target domain’s DNS, you’re not really in control of the load balancing.

Why Use DNS Round Robin Load Balancing?

So why would you want to use DNS round robin load balancing in the first place?

Here’s why it’s useful:

• It’s free – No extra hardware, no paid services. Just configure your DNS.
• It’s easy to set up – You don’t need to be a network engineer to add a few A records.
• It helps spread traffic – Even if not perfectly balanced, it does reduce the load on each server.
• It adds basic redundancy – If one server goes down, users might still reach the others.

Now, it’s not perfect. There’s no health checking. If one IP is down, DNS will still give it out unless you manually remove it. But if you’re okay with a basic setup, round-robin server rotation can work just fine.

How to Set Up Round Robin DNS

You don’t need anything fancy. If you’re managing DNS through a provider like Cloudflare, Namecheap, Route 53, or even cPanel, here’s what you do:

1. Go to your domain’s DNS settings.
2. Add multiple A records for the same hostname:
   
   yourdomain.com → 203.0.113.1 
   yourdomain.com → 203.0.113.2 
   yourdomain.com → 203.0.113.3  
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3. Save changes. That’s it.

Now when a user resolves your domain, they’ll get a list of all three. The order may rotate depending on the DNS resolver, but in most cases, users will be spread across the three IPs over time.

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Limitations of DNS Round Robin

Let’s be honest—it’s not magic. Here’s where DNS round robin starts to fall short:

• No server health checks – If one server is down, users might still get routed there.
• Uneven distribution – Some clients always pick the first IP. Some ISPs cache results.
• No session stickiness – Every DNS lookup can return a different IP, which can break apps that expect persistent connections.
• No smart routing – It’s not aware of traffic load, server performance, or user location.

It’s basic. But sometimes, basic is all you need.

What If Round Robin Isn't Working?

So you've set up your round robin server rotation with multiple DNS A records, but something feels off. One server gets all the traffic, or worse, a dead one is still being handed out. 

Here's what's probably going wrong:

• Your DNS resolver is caching results too long.
  If the TTL (Time to Live) on your A records is high, users may hit the same IP repeatedly. Lower it to 30–60 seconds for more frequent cycling.
• Some resolvers always prefer the first IP.
  Not all DNS resolvers respect the round-robin order. Some sort the list. Some just pick the first. It’s out of your control.
• A server is down—but DNS doesn’t know.
  Round-robin DNS doesn’t do health checks. If one IP isn’t responding, the user has to wait for a browser timeout or retry another IP manually.
• Your app breaks without session persistence.
  If your app expects users to stay on the same server, round robin can mess with that, especially on reconnects.

Quick Fixes:

• Use short TTLs (but don’t go crazy—under 30s can backfire).
• Add server-side logic or load balancers to catch failures.
• For production apps, consider smarter DNS or full-fledged load balancing.

When Should You Use It?

Here’s when round robin DNS makes sense:

• You’re running multiple stateless web servers.
• You want quick-and-dirty load balancing for internal tools or microservices.
• You don’t need failover or perfect uptime, but want to ease traffic across servers.
• You’re hosting a low-risk app or a side project.

Avoid it if you’re running mission-critical systems or apps with stateful sessions, payments, or anything sensitive. In those cases, go for a proper load balancer or reverse proxy setup.

Round Robin DNS vs. Other Load Balancing Methods

Let’s keep it simple:

Round robin is the DIY starter pack. It’s good if you know the trade-offs.

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Round Robin DNS and CDNs – Can They Work Together?

If you’re using a CDN like Cloudflare, Fastly, or Bunny.net, you might be wondering: can I still use DNS round robin load balancing?

The answer depends on how your CDN is set up.

Most CDNs act as the authoritative DNS for your domain. That means your round robin logic—those multiple A records—needs to be configured inside your CDN dashboard, not with your domain registrar.

Here’s where it gets tricky:

Many CDNs don’t support basic round-robin server rotation at the DNS level. Instead, they offer smarter routing options like:

• Geo-routing (send users to the closest server)
• Weighted load balancing
• Failover logic with health checks

These features are more powerful than round robin—but they usually live behind a paywall.

Heads up: If you're using a CDN, test everything. You may be unintentionally overriding your round-robin setup without realizing it.

Conclusion

If you just want to split traffic between servers and don’t need precision, round-robin DNS is a great tool to have in your pocket. It’s dead simple, uses nothing but DNS A records, and can get you up and running with a basic DNS multiple A records setup in minutes.

Just remember: it’s a blunt tool. Use it where it fits. And if your app grows, don’t be afraid to switch to more robust solutions.

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