Couple of explanations here:
First, I'm assuming a couple of things:
1. User accounts exist both on the local machine and the domain controller.
2. The same user ID and password (credentials) are used for both the local computer user account and the domain user account.
NT uses a concept called pass-through authentication. This works as follows: A user provides a set of credentials at the local login. Later the user attempts to access a network resource requiring domain credentials.The PDC will query the local computer for the credentials provided at log-on. If the credentials match a valid domain user accout, the local credentials are accepted as valid and access is granted.
The main effect this will have on your network operations is that since the user is logging on locally, no domain security policies or log-on scripts are passed on and applied at log-on.
To take this a step further:
Even if credential do not match, there is still a method to access network resources (shared drives). When using the Map Network Drive tool to map a shared resource (vs. mapping a shared drive by going through Network Neighborhood), a user is provided the ability to connect using a different set of credentials. The user canthen provide his domain credentials to gain access to shared resources, even though he is only logg-on locally with different credentials.
Hope this clears things up a little.
