Round-robin DNS is a simple load distribution method: a name has multiple address records, and the server rotates the order of the answers on each query. Clients usually try the first address, so traffic is spread roughly evenly.
Why it matters
It costs nothing and needs no extra hardware, so it is common for small clusters, mail exchangers and simple redundancy. It is not a true load balancer. DNS does not know whether a server is healthy, how busy it is or how many users sit behind a caching resolver. A dead server keeps receiving a share of requests until you remove its record and the TTL expires. Some clients retry the next address on a failed connection, which softens the effect.
Example
$ dig +short www.example.com
203.0.113.11
203.0.113.12
203.0.113.13A second query may return the same three records in a different order.
Common mistakes
- Treating it as high availability. With no health checks, failures stay in rotation.
- Assuming an even split. Large resolvers cache one order for many users.
- Using it for stateful applications without shared sessions.
Related
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