Set the dbx environment variable core_lo_pathmap to on.
Use the pathmap command to tell dbx where the correct libraries for the core file are located.
Use the debug command to load the program and the core file.
For example, assuming that the root partition of the core-host has been exported over NFS and can be accessed via /net/core-host/ on the dbx-host machine, you would use the following commands to load the program prog and the core file prog.core for debugging:
(dbx) dbxenv core_lo_pathmap on (dbx) pathmap /usr /net/core-host/usr (dbx) pathmap /appstuff /net/core-host/appstuff (dbx) debug prog prog.core
If you are not exporting the root partition of the core-host, you must copy the libraries by hand. You need not re-create the symbolic links. (For example, you need not make a link from libc.so to libc.so.1; just make sure libc.so.1 is available.)