A Mac can connect to a Windows network without running Windows, as routers and switches do not depend on the operating system of connected devices. The key factor for compatibility is the use of the same communication protocol, such as TCP/IP. For basic internet access, the operating system is not relevant. However, for tasks like authenticating against a Windows Active Directory network or accessing shared files, compatibility becomes important. Macs have built-in support for Windows networks, allowing for file sharing and access to Windows domains using protocols like SMB. Higher-level protocols are necessary for communication between different operating systems, with LDAP being a standard for querying Active Directory, though it is primarily for information retrieval rather than authentication. Compatibility issues often arise due to non-standard practices by major companies, particularly Microsoft.