How to DNS load balancing works

When the request comes to the DNS server to resolve the domain name, it gives out one of the

Several canonical names in a rotated order. This redirects the request to one of the several SERVERS in a server group. Once the BIND feature of DNS resolves the domain to one of the servers, subsequent requests from the same client are sent to the same server.

DNS load balancing implementation (Multiple CNAMES)

This approach works for BIND 4 name servers, where multiple CNAMES are not considered as a configuration error. Assuming there are 4 web servers in the cluster configured with IP addresses 123.45.67.[1-4], add all of them to the DNS with Address records (A Names) as below. The srv[1-4] can be set to any name you want, such as foot[1-4], but should match the next step.

The DNS server will resolve the www.domain.com to one of the listed servers in a rotated manner. That will spread the requests over the group of servers.