This behaviour is a result of the upstream fix for upstream bug 2997. It is still present in all Squid-3 (will be fixed in Squid-4). When Squid is assigned an explicit listening IP and that IP has reverse-DNS it is used instead of halting startup.
Only the first http_port or https_port is checked in the affected versions. To prevent localhost being used, do not configure it as the primary listening address for Squid.
This behaviour is a result of the upstream fix for upstream bug 2997. It is still present in all Squid-3 (will be fixed in Squid-4). When Squid is assigned an explicit listening IP and that IP has reverse-DNS it is used instead of halting startup.
Only the first http_port or https_port is checked in the affected versions. To prevent localhost being used, do not configure it as the primary listening address for Squid.