Oracle 11.2.0.1 - ORA-12545:Connect failed because target host or object does not exist

Dear all.

I have one database version 11.2.0.1 - install on CentOS release 6.6 (Final).

When i try login database by command line with command:

sqlplus / as sysdba

or

sqlplus /nolog
conn system/password
I have receive message

ERROR:

ORA-12545: Connect failed because target host or object does not exist

These some information for database system

cat /etc/hosts

10.79.74.137 serverdb

127.0.0.1    localhost.localdomain localhost4 localhost4.localdomain4   serverdb

::1                     serverdb.localdomain        localhost.localdomain   localhost6      localhost6.localdomain6 localhost      serverdb

cat $ORACLE_HOME/network/admin/tnsnames.ora

DB11G =

  (DESCRIPTION =

    (ADDRESS_LIST =

      (ADDRESS = (PROTOCOL = TCP)(HOST = serverdb)(PORT = 1522))

    )

    (CONNECT_DATA =

      (SERVER = DEDICATED)

      (SERVICE_NAME = db11g)

    )

  )

cat $ORACLE_HOME/network/admin/listener.ora