Authentication via 'hostapd_cli' against an external RADIUS server

Hi,

My AP is running

    # hostapd /etc/hostapd.conf -dd
    random: Trying to read entropy from /dev/random
    Configuration file: /etc/hostapd.conf
    ctrl_interface_group=0
    eapol_version=2
    Opening raw packet socket for ifindex 2
    BSS count 1, BSSID mask 00:00:00:00:00:00 (0 bits)
    Using existing control interface directory.
    ctrl_iface bind(PF_UNIX) failed: Address already in use
    ctrl_iface exists, but does not allow connections - assuming it was
    leftover from forced program termination
    Successfully replaced leftover ctrl_iface socket '/var/run/hostapd/eth0'
    eth0: IEEE 802.11 Fetching hardware channel/rate support not supported.
    Completing interface initialization
    hostapd_setup_bss(hapd=0xdb220 (eth0), first=1)
    eth0: Flushing old station entries
    eth0: Deauthenticate all stations
    Using interface eth0 with hwaddr 00:30:d6:18:45:86 and ssid ""
    eth0: RADIUS Authentication server 192.168.200.120:1812
    RADIUS local address: 192.168.200.236:39631
    eth0: interface state UNINITIALIZED->ENABLED
    eth0: AP-ENABLED
    eth0: Setup of interface done.
    ctrl_iface not configured!
    random: Got 20/20 bytes from /dev/random

How can I authenticate via 'hostapd_cli' against an external RADIUS server?

Thanks,

Erwin