In RedHat Enterprise Linux 7, the sssd daemons can connect to active directory servers. Default behaviour is to update DNS entries dynamically.
If a statical DNS entry already exists this can lead to a CPU consuming sssd_nss daemon.
To prevent this behaviour, the dynamic DNS updates should be switched off with this setting in every doman section of config file /etc/sssd/sssd.conf:
dyndns_update = False
After that sssd should be restarted to take this change effect.