The ancontrol utility controls the
operation of Aironet wireless networking devices via the
an(4)
driver. Most of the parameters that can be changed relate to the IEEE 802.11
protocol which the Aironet cards implement. This includes such things as the
station name, whether the station is operating in ad-hoc (point to point) or
infrastructure mode, and the network name of a service set to join. The
ancontrol utility can also be used to view the
current NIC status, configuration and to dump out the values of the card's
statistics counters.
The iface argument given to
ancontrol should be the logical interface name
associated with the Aironet device (an0,
an1, etc.). If one is not specified the device
“an0” will be assumed.
The ancontrol utility is not designed to
support the combination of arguments from different
SYNOPSIS lines in a single
ancontrol invocation, and such combinations are not
recommended.
Display the preferred access point list. The AP list can be used by
stations to specify the MAC address of access points with which it wishes
to associate. If no AP list is specified (the default) then the station
will associate with the first access point that it finds which serves the
SSID(s) specified in the SSID list. The AP list can be modified with the
-a option.
Display the SSID list. This is a list of service set IDs (i.e., network
names) with which the station wishes to associate. There may be up to
three SSIDs in the list: the station will go through the list in ascending
order and associate with the first matching SSID that it finds.
Display NIC status information. This includes the current operating
status, current BSSID, SSID, channel, beacon period and currently
associated access point. The operating mode indicates the state of the
NIC, MAC status and receiver status. When the
"synced" keyword appears, it means the
NIC has successfully associated with an access point, associated with an
ad-hoc “master” station, or become a “master”
itself. The beacon period can be anything between 20 and 976 milliseconds.
The default is 100.
Display current NIC configuration. This shows the current operation mode,
receive mode, MAC address, power save settings, various timing settings,
channel selection, diversity, transmit power and transmit speed.
Display the cached signal strength information maintained by the
an(4) driver. The driver retains information about signal strength
and noise level for packets received from different hosts. The signal
strength and noise level values are displayed in units of dBms by default.
The hw.an.an_cache_modesysctl(8) variable can be set to raw,
dbm or per.
Set preferred access point. The AP is specified as a
MAC address consisting of 6 hexadecimal values separated by colons. By
default, the -a option only sets the first entry
in the AP list. The -v modifier can be used to
specify exactly which AP list entry is to be modified. If the
-v flag is not used, the first AP list entry will
be changed.
Select the antenna diversity. Aironet devices can be configured with up to
two antennas, and transmit and receive diversity can be configured
accordingly. Valid selections are as follows:
The receive and transmit diversity can be set independently.
The user must specify which diversity setting is to be modified by using
the -v option: selection
0 sets the receive diversity and
1 sets the transmit diversity.
Set the transmit WEP key to use. Note that until this command is issued,
the device will use the last key programmed. The transmit key is stored in
NVRAM. Currently set transmit key can be checked via
-C option. Selection 4
sets the card in “Home Network Mode” and uses the home
key.
Set a WEP key. For 40 bit prefix 10 hex character with 0x. For 128 bit
prefix 26 hex character with 0x. Use "" as the key to erase the
key. Supports 4 keys; even numbers are for permanent keys and odd number
are for temporary keys. For example, -v1 sets the first temporary key. (A
“permanent” key is stored in NVRAM; a
“temporary” key is not.) Note that the device will use the
most recently-programmed key by default. Currently set keys can be checked
via -C option, only the sizes of the keys are
returned. The value of 8 is for the home key. Note
that the value for the home key can be read back from firmware.
Set the ad-hoc network join timeout. When a station is first activated in
ad-hoc mode, it will search out a “master” station with the
desired SSID and associate with it. If the station is unable to locate
another station with the same SSID after a suitable timeout, it sets
itself up as the “master” so that other stations may
associate with it. This timeout defaults to 10000 milliseconds (10
seconds) but may be changed with this option. The timeout should be
specified in milliseconds.
Set the station name used internally by the NIC. The
station_name can be any text string up to 16
characters in length. The default name is set by the driver to
“FreeBSD”.
Set the station address for the specified interface. The
mac_address is specified as a series of six
hexadecimal values separated by colons, e.g.:
00:60:1d:12:34:56. This programs the new address
into the card and updates the interface as well.
Set the desired SSID (network name). There are three SSIDs which allows
the NIC to work with access points at several locations without needing to
be reconfigured. The NIC checks each SSID in sequence when searching for a
match. The SSID to be changed can be specified with the
-v modifier option. If the
-v flag is not used, the first SSID in the list is
set.
Set the operating mode of the Aironet interface. Valid selections are
0 for ad-hoc mode and 1
for infrastructure mode. The default driver setting is for infrastructure
mode.
Set the transmit power level in milliwatts. Valid power settings vary
depending on the actual NIC and can be viewed by dumping the device
capabilities with the -I flag. Typical values are
1, 5, 20, 50 and 100mW. Selecting 0 sets the factory default.
Set the radio frequency of a given interface. The
frequency should be specified as a channel ID as
shown in the table below. The list of available frequencies is dependent
on radio regulations specified by regional authorities. Recognized
regulatory authorities include the FCC (United States), ETSI (Europe),
France and Japan. Frequencies in the table are specified in MHz.
If an illegal channel is specified, the NIC will revert to its
default channel. For NICs sold in the United States and Europe, the
default channel is 3. For NICs sold in France, the default channel is
11. For NICs sold in Japan, the only available channel is 14. Note that
two stations must be set to the same channel in order to
communicate.
Set the fragmentation threshold in bytes. This threshold controls the
point at which outgoing packets will be split into multiple fragments. If
a single fragment is not sent successfully, only that fragment will need
to be retransmitted instead of the whole packet. The fragmentation
threshold can be anything from 64 to 2312 bytes. The default is 2312.
Set the RTS/CTS threshold for a given interface. This controls the number
of bytes used for the RTS/CTS handshake boundary. The
RTS_threshold can be any value between 0 and 2312.
The default is 2312.
WEP (“wired equivalent privacy”) is based on the RC4
algorithm, using a 24 bit initialization vector.
RC4 is supposedly vulnerable to certain known plaintext attacks,
especially with 40 bit keys. So the security of WEP in part depends on how
much known plaintext is transmitted.
Because of this, although counter-intuitive, using “shared
key” authentication (which involves sending known plaintext) is less
secure than using “open” authentication when WEP is
enabled.
Devices may alternate among all of the configured WEP keys when
transmitting packets. Therefore, all configured keys (up to four) must
agree.
The statistics counters do not seem to show the amount of transmit
and received frames as increasing. This is likely due to the fact that the
an(4)
driver uses unmodified packet mode instead of letting the NIC perform
802.11/ethernet encapsulation itself.
Setting the channel does not seem to have any effect.