add standby listener

 Hi,

    How do I add standby listener to same port. I have lines as follows for current listener.

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = ORCL)
      (ORACLE_HOME = /opt/oracle/product/11.1.0)
      (SID_NAME = ORCL)
    )
  )

LISTENER =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = hostname.domain)(PORT = 1521))
  )

Thanks,

Arun