web server fail-over

Hi everyone, I am trying to setup a primary web server and a backup web server. I want to create an automatic fail-over so when the primary web server go down, the backup server will be available immediately but it will be available only when the primary server is not available. I don’t want to do round-robin and I cannot setup Microsoft clustering server. I am looking for hardware solution such as managed switch or something similar. I appreciate if anyone has any suggestion