Dear All, The problem under discussion is a continutity of SPN creation/Single Forest MultiDomain (Active Directory) topic. @ Markus Yes my infrastructure is Active Directory based (Root Forest Directory A with two child domains B (80 % users) & C (20 % users) in their own trees). Only squid Proxy is installed on Centos OS and not joined to any domain.Markus you are right I Observerd that the clients in the child domain are able to use squidproxy without any changes required in the krb5.conf file.(no need to define [CAPATH] section). I got it that by design of the Active directory forest where Parent domains and child domains have two way transitive trusts, Active directory/DNS infrastructure is managing itself...and the clients in any domain are able to find that Service principal is in which domain to acquire a service ticket from that domain. Right?? If the UnixServer(Proxy) is not belonged to any domain then the default_realm section does not matter and i can choose any of my domains as default_realm. As i think that the default_realm tag is compulsory to define so couldn't be left blank. Similarly if am not to use any other kerberised service for example from my SquidProxyunix server then .linux.home tag will be unimportant otherwise it is a must. Right?? //krb5.conf for Active directory single forest multi domain its working correctly-------------------------------------------- [libdefaults] default_realm = A.COM.PK dns_lookup_realm = false dns_lookup_kdc = false default_keytab_name = /etc/krb5.keytab ; for windows 2003 encryption type configuration. default_tgs_enctypes = rc4-hmac des-cbc-crc des-cbc-md5 default_tkt_enctypes = rc4-hmac des-cbc-crc des-cbc-md5 permitted_enctypes = rc4-hmac des-cbc-crc des-cbc-md5 [realms] A.COM.PK = { kdc = dc1.a.com.pk admin_server = dc1.a.com.pk } b.A.COM.PK = { kdc = childdc.b.a.com.pk admin_server = childdc.b.a.com.pk } [domain_realm] .linux.home = A.COM.PK .a.com.pk = A.COM.PK a.com.pk = A.COM.PK .b.a.com.pk = b.A.COM.PK b.a.com.pk = b.A.COM.PK [logging] kdc = FILE:/var/log/kdc.log admin_server = FILE:/var/log/kadmin.log default = FILE:/var/log/kdc.log ----------------\\ Any suggestions/guidance required?? My squid.conf portion related to Authentication/Authorization along with the questions. auth_param negotiate program /usr/libexec/squid/squid_kerb_auth auth_param negotiate children 10 auth_param negotiate keep_alive on # basic auth ACL controls to make use of it are. #acl auth proxy_auth REQUIRED #http_access deny !auth #http_access allow auth I think now above commented directives are not required as squid_kerb_ldap has taken the charge. Right??? #external_acl_type squid_kerb1 ttl=3600 negative_ttl=3600 %LOGIN /usr/libexec/squid/squid_kerb_ldap -g GROUP1@xxxxxxxx:GROUP2@xxxxxxxx:GROUP3@xxxxxxxx:G1@xxxxxxxxxx:GROUP2@xxxxxxxxxx:GROUP3@xxxxxxxxxx external_acl_type g1_parent ttl=3600 negative_ttl=3600 %LOGIN /usr/libexec/squid/squid_kerb_ldap -g GROUP1@xxxxxxxx external_acl_type g2_parent ttl=3600 negative_ttl=3600 %LOGIN /usr/libexec/squid/squid_kerb_ldap -g GROUP2@xxxxxxxx external_acl_type g2_child ttl=3600 negative_ttl=3600 %LOGIN /usr/libexec/squid/squid_kerb_ldap -g GROUP2@xxxxxxxxxx Although the commented single liner was working properly for me and look more apporpriate to me but i had to split it into multiple lines....nothing came into my mind how to handle the ACL's based on user group membership. Please guide me if there is a better way to do that as it feels that i am calling the helper multiple times instead of single time now?? (There are other expected groups from child domains and parent domains so am worried that isnt it affect the performance) acl ldap_group_check1 external g1_parent acl ldap_group_check2 external g2_parent acl ldap_group_check3 external g2_child ####Definition of YouTube. ## The videos come from several domains acl youtube_domains dstdomain .youtube.com .googlevideo.com .ytimg.com http_access deny ldap_group_check1 youtube_domains http_access allow ldap_group_check2 http_access allow ldap_group_check1 http_access allow ldap_group_check3 http_access deny all As i think squid.conf file is parsed from top to bottom and if a related statement/acl is met then will see no further so it means that putting the statments in an order where groups containing most of the users will improve performance. Can there be if-else structure be used in squid.conf and how? Am not sure??? please guide... Thanking you & regards, Bilal _________________________________________________________________ Hotmail: Free, trusted and rich email service. https://signup.live.com/signup.aspx?id=60969