NameVirtualHost *:80

<VirtualHost *:80>
  ServerName sub1.domain1.com
</VirtualHost>

<VirtualHost *:80>
  ServerName sub2.domain1.com
</VirtualHost>

<VirtualHost *:80>
  ServerName domain1.com
  ServerAlias *.domain1.com
</VirtualHost>

<VirtualHost *:80>
  ServerName sub1.domain2.com
</VirtualHost>

<VirtualHost *:80>
  ServerName sub2.domain2.com
</VirtualHost>

<VirtualHost *:80>
  ServerName domain2.com
  ServerAlias *.domain2.com
</VirtualHost>