Your keytab has DOMAIN.ORG as the realm.
Your log has NAT.DOMAIN.ORG
And your sssd.conf has: NAT.C.SDU.DK
What is the realtionship between the realms?
Sorry , I send the wrong file - this is the right one, corresponding to the log file:
cat /etc/sssd/sssd.conf [nss] debug_level = 9 filter_groups = root filter_users = root,lightdm,ldap,named,avahi,haldaemon,dbus,radvd,tomcat,radiusd,news,mailman,nscd
[sssd] debug_level = 7 domains =nat.domain.org config_file_version = 2 services = nss, pam
[domain/nat.domain.org] debug_level = 7 ad_domain = nat.domain.org krb5_realm = NAT.DOMAIN.ORG realmd_tags = manages-system joined-with-samba cache_credentials = True id_provider = ad auth_provider = ad access_provider = ad krb5_store_password_if_offline = True default_shell = /bin/bash ldap_id_mapping = False use_fully_qualified_names = True fallback_homedir = /home/%d/%u # dyndns_update = true