Why do I get errors during Analysis & Synthesis when using multiple IP cores?

Description

If you compile a design with multiple IP cores, you may encounter the errors below:

Error (12179): Instance "<instance name>" is ambiguous File: <file name>, Line:< line number>
    Error (12180): Instance could be entity <entity name> in file <file name> compiled in library <first library name> File: <file name>, Line:< line number>
   Error (12180): Instance could be entity "<entity name>" in file <file name> compiled in library <second library name> File: <file name>, Line:< line number>

Resolution

These errors indicate a conflict in files generated for multiple IP cores. Each IP core should be compiled into its own design library as indicated in its Quartus II IP (.qip) file.

If you see these errors, verify that your Quartus II Settings File (.qsf) file only calls out the .qip files for each IP core. You should not include any of the files listed in the .qip file directly in the .qsf.