Hey Max, You are using squid 3.1.x which is not supported anymore by the squid development team. It is possible that there is a bug in this version of squid and that it was not reported until now. Squid should not run a PTR record lookup unless there is an acl which requires\wants\needs it. Details on squid for CentOS at: http://wiki.squid-cache.org/KnowledgeBase/CentOS In any case the better place to seek for an answer on the issue you have described is in the squid-users mailing list. All The Bests, Eliezer Croitoru On 31/01/2015 20:36, Max Grobecker wrote: > Is anyone else experiencing this? It seems to be happen on IPv6 client addresses only - with IPv4 it works just fine. > And besides of these broken PTR lookups Squid is working as expected. > > > > Greetings from Wuppertal > Max