DNS round-robin definition
DNS round-robin is a simple technique that provides load balancing, load distribution, or fault tolerance for DNS servers. DNS round-robin uses multiple identically configured servers to distribute incoming traffic evenly among them, which reduces the load on each server and improves the efficiency of the network.
All servers use the same domain name, but each has an individual IP address associated with the said domain. This allows servers that have DNS round-robin enabled to respond to requests in a rotating manner, handing out a different address each time. For instance, the first request gets the IP address of the first server, the second one gets the IP of the second server, and so on. Basically, each IP address and server gets a chance to respond to a request and is then moved to the back of the line to wait for its next turn.
See also: round robin DNS, DNS server, DNS query, DNS resolution, DNS client, DNS cache, DNS hijacking, DNS proxy, DNS failover
How DNS round-robin works
- 1.Multiple IP addresses configured. A single domain name is configured with multiple IP addresses in the DNS records, each pointing to a different server.
- 2.DNS server rotates responses. When a query is received, the DNS server returns the IP addresses in a rotating order, distributing each new request to a different server.
- 3.Client connects to assigned server. The client receives an IP address and connects to that specific server, with subsequent requests directed to other servers in the rotation.
DNS round-robin drawbacks
- The combination of DNS caching and client-side caching can be challenging to manage, which means that DNS round-robin cannot always provide load balancing.
- If one server fails, the DNS will still give out that server’s address in the rotation, and clients that get that IP will not be able to reach the service they are looking for.
