hi Markus, Please see the below. I just temporally change access control of keytab file. Still no lucky [root@proxy01 squid]# ls -al total 76 drwxr-xr-x. 2 root root 4096 Dec 23 14:24 . drwxr-xr-x. 105 root root 12288 Dec 24 11:18 .. -rw-r--r--. 1 root squid 419 Oct 1 23:40 cachemgr.conf -rw-r--r--. 1 root root 419 Oct 1 23:40 cachemgr.conf.default -rw-r--r--. 1 root root 1547 Oct 1 23:40 errorpage.css -rw-r--r--. 1 root root 1547 Oct 1 23:40 errorpage.css.default -rw-r--r--. 1 root root 11651 Oct 1 23:40 mime.conf -rw-r--r--. 1 root root 11651 Oct 1 23:40 mime.conf.default -rw-r--r--. 1 root root 421 Oct 1 23:40 msntauth.conf -rw-r--r--. 1 root root 421 Oct 1 23:40 msntauth.conf.default -rw-r-----. 1 root squid 2758 Dec 23 14:24 squid.conf -rw-r--r--. 1 root root 2510 Oct 1 23:40 squid.conf.default *-rwxrwxrwx. 1 root squid 451 Dec 22 13:13 squid.keytab* In addition. [root@proxy01 etc]# kinit -kt ./squid/squid.keytab HTTP/proxy02.deeplayer.com [root@proxy01 etc]# klist -ekt ./squid/squid.keytab Keytab name: FILE:./squid/squid.keytab KVNO Timestamp Principal ---- ----------------- -------------------------------------------------------- 16 12/22/13 13:14:31 proxy02$@DEEPLAYER.COM (arcfour-hmac) 16 12/22/13 13:14:31 proxy02$@DEEPLAYER.COM (aes128-cts-hmac-sha1-96) 16 12/22/13 13:14:31 proxy02$@DEEPLAYER.COM (aes256-cts-hmac-sha1-96) 16 12/22/13 13:14:31 HTTP/proxy02.deeplayer.com@xxxxxxxxxxxxx (arcfour-hmac) 16 12/22/13 13:14:31 HTTP/proxy02.deeplayer.com@xxxxxxxxxxxxx (aes128-cts-hmac-sha1-96) 16 12/22/13 13:14:31 HTTP/proxy02.deeplayer.com@xxxxxxxxxxxxx (aes256-cts-hmac-sha1-96) [root@proxy01 etc]# -- View this message in context: http://squid-web-proxy-cache.1019090.n4.nabble.com/squid-proxy-kerberos-authentication-failure-Help-tp4663964p4664010.html Sent from the Squid - Users mailing list archive at Nabble.com.