RMAN-04004: error from recovery catalog database: ORA-28040: No matching authentication protocol

My oracle database: 9i  on HP-UX

My Catalog database: 12c on RHEL 6

Today while taking RMAN backup from backup tool we are getting below error

[Major] From: ob2rman@myoradec01.domain.com"prod"  Time: 10/15/16 17:03:34

                The database reported error while performing requested operation.

RMAN-00571: ===========================================================

 RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

 RMAN-00571: ===========================================================

 RMAN-04004: error from recovery catalog database: ORA-28040: No matching authentication protocol

I wanted to try connecting from the server to the catalog database

Myoradev01:prod:/opt/oracle/product/9.2.0.8.64/network/admin $ rman target /

Recovery Manager: Release 9.2.0.8.0 - 64bit Production

Copyright (c) 1995, 2002, Oracle Corporation.  All rights reserved.

connected to target database: PROD (DBID=176732808)

RMAN> connect catalog prod_user/xxxx@rcvc

RMAN-00571: ===========================================================

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

RMAN-00571: ===========================================================

RMAN-04004: error from recovery catalog database: ORA-28040: No matching authentication protocol

RMAN>

According to oracle 

 “Connections to a 12c database server can only be made from a 10.2 and later client.”

But if you make changes to sqlnet.ora on the catalog it will work, to do so go to catalog database and modify $ORACLE_HOME/network/admin/sqlnet.ora file as below

audbs1:rm:/opt/oracle/product/12.1.0.2.64/network/admin $ vi sqlnet.ora

AUTOMATIC_IPC=ON

SQLNET.INBOUND_CONNECT_TIMEOUT=0

SQLNET.ALLOWED_LOGON_VERSION_SERVER = 8  à ADDED this Line

 Try to connect to catalog database again from 9i database

Myoradev01:prod:/opt/oracle/product/9.2.0.8.64/network/admin $ rman target /

Recovery Manager: Release 9.2.0.8.0 - 64bit Production

Copyright (c) 1995, 2002, Oracle Corporation.  All rights reserved.

connected to target database: PROD (DBID=176732808)

RMAN> connect catalog prod_user/xxxx@rcvc

connected to recovery catalog database

Now I can able to connect and my Issue is resolved.

Refer:

RMAN Catalog (12c) Connection Failed For 9.2.0.6.0 Database (Doc ID 1922190.1)