Option Name:dns_v4_first
Default Value:dns_v4_first off
Suggested Config:

	With the IPv6 Internet being as fast or faster than IPv4 Internet
	for most networks Squid prefers to contact websites over IPv6.

	This option reverses the order of preference to make Squid contact
	dual-stack websites over IPv4 first. Squid will still perform both
	IPv6 and IPv4 DNS lookups before connecting.

	  This option will restrict the situations under which IPv6
	  connectivity is used (and tested). Hiding network problems
	  which would otherwise be detected and warned about.