Safe to use SQLNET.ALLOWED_LOGON_VERSION_SERVER in 11g sqlnet.ora file?
The parameter exists in 11g as well. This is the 11g documentation:

SQLNET.ALLOWED_LOGON_VERSION


  Allowed Values
  
  
  12 for the critical patch updates CPUOct2012 and later Oracle Database
  11g authentication protocols (recommended)
  11 for Oracle Database 11g authentication protocols
  10 for Oracle Database 10g authentication protocols
  9 for Oracle9i Database authentication protocols
  8 for Oracle8i Database authentication protocols (default)