If you set some domain as default for an IP with the Server ->; IP Addresses ->; Hosting ->; Set As Default and wish to revet this back, use the command:
cat /etc/psa/.psa.shadow mysql -uadmin -nBe 'update IP_Addresses set default_domain_id=0 where ip_address="IP_ADDRESS"' psa``
Then rebuild Apache configuration files with the "PRODUCT_ROOT_D/admin/sbin/websrvmng -a -v" command.
IP_ADDRESS - Shoud be replaced by real IP address from the server.
Here you can find our how to set default domain for IP address.