Can you please let me know if there are any function modules/Bapi's to create Classification data for a Routing?
For creating classification data, have a look at the function group CTMS and function module CTMS_DDB_SET_VALUE_INTERNAL.
Not sure what you mean by "Routing".
For BAPIs also look into the function group CLBPA, that sits in the same development package CLCL as the function group CTMS.
Hope this helps.