TNS-12508: TNS:listener could not resolve the COMMAND given

Getting below TNS error while changing the trace level for the listener

LSNRCTL> set trc_level user
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROCEBSSBX_SSL)))
TNS-12508: TNS:listener could not resolve the COMMAND given


Fix:
===
Turn off the ADMIN_RESTRICTIONS in listener.ora

cat listener.ora | grep -i restrictions
ADMIN_RESTRICTIONS_RAC1DB =  ON

change it to:
ADMIN_RESTRICTIONS_RAC1DB =  OFF

LSNRCTL> stop RAC1DB
LSNRCTL> start RAC1DB

or
[oracle@rac1 ~]$ lsnrctl stop racdb1db

LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 14-JUL-2017 10:51:24

Copyright (c) 1991, 2009, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac1.localdomain.com)(PORT=1522)))
The command completed successfully
[oracle@rac1 ~]$ lsnrctl start rac1db

Now try to reset the trace level:
=====================

LSNRCTL> set current_listener rac1db
Current Listener is rac1db

LSNRCTL> set trc_level off
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac1.localdomain.com)(PORT=1522)))
rac1db parameter "trc_level" set to off
The command completed successfully

LSNRCTL> save_config
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=rac1.localdomain.com)(PORT=1522)))
Saved rac1db configuration parameters.
Listener Parameter File   /u01/app/oracle/product/11.2.0.2/db_home/network/admin/listener.ora
Old Parameter File   /u01/app/oracle/product/11.2.0.2/db_home/network/admin/listener.bak
The command completed successfully