Balance is a free version of load balancing created by Inlab in Germany. I am trying to setup Balance on my Ubuntu Server and hit this error Balance unable to start (“setsockopt(IPV6_V6ONLY=0): Protocol not available) when I issue the balance command. After digging around, I found the following solution which actually worked for me. So I am sharing it for everyone who encounters this issue.

This problem isn’t fixed in the latest versions, the change appears that balance now needs IPv6 addresses if you specify IP addresses (versus host names). to fix this problem for v4 addresses add ::ffff: to the beginning of your address. for example:

balance -b 192.168.1.2 631 spiffycupshost

(which gives you this error)
should now become:
balance -b ::ffff:192.168.1.2 631 spiffycupshost

and the error will go away.

Provided by Craig Sawyer