title: Unable to connect through SQLPLUS from a oracle client 11g to 18c database
body: <p>There are a few topics on web about connecting issue from 11g to 18c, sqlplus vs sqldeveloper and etc, but not a combination of all.  Here's the question:</p>
  
  <p>I'm trying to connect to a 18c Oracle database via sqlplus (11g 32-bit client) from my PC.  All of the below works:  </p>
  
  <pre><code>1) connect via Mobaxterm (as oracle) from my PC that has 18.0.0.0 client  
  2) connect via sqldeveloper, with both SID / service name option tested  
  3) TNSPING from my PC to the 18c DB (i.e. tnsname.ora is good)  
  4) sqlplus works from my PC to another 11g oracle DBs  
  </code></pre>
  
  <p>Only thing that does not works is the combination of sqlplus from 11g 32bit client to 18c database.  The error is </p>
  
  <pre><code>invalid username/password; logon denied.  
  </code></pre>
  
  <p>Same credential is used throughout the testing (which worked on 1) and 2) above).  I made sure:</p>
  
  <pre><code>A) These are added to the sqlnet.ora:  
  SQLNET.ALLOWED_LOGON_VERSION_SERVER=11  
  SQLNET.ALLOWED_LOGON_VERSION_CLIENT=11  
  
  B) Oracle_SID is pointing to the correct name
  
  C) sqlplus is run from CMD as administrator
  </code></pre>
  
  <p>Please let me know if i should provide more info.<br>
      Thanks in advance.</p>