Enterprise Manager DB Control/DB Console (OEM) is not working after Changing Hostname or IP Address

After change hostname on oracle linux 6, enterprise manager doesn't working, for solve this problem make next steps:
1) Set $ORACLE_HOSTNAME to the old hostname

export ORACLE_HOSTNAME=old_name

2) De-configure the old DB Console by running the following command:

$ORACLE_HOME/bin/emca -deconfig dbcontrol db

3) Set $ORACLE_HOSTNAME to the new hostname:

export ORACLE_HOSTNAME=new_name

4)Configure the new DB Console

$ORACLE_HOME/bin/emca -config dbcontrol db -repos recreate