CDK Global touts itself as an all-in-one software-as-a-service solution that is "trusted by nearly 15,000 dealer locations." One connection, over an always-on VPN to CDK's data centers, gives a dealership customer relationship management (CRM) software, financing, inventory, and more back-office tools. That all-in-one nature explains why people trying to buy cars, and especially those trying to sell them, have had a rough couple of days.