Examine the IEEE 802.11 wireless LAN client/peer table
Syntax:
wlanctl interface [...]
wlanctl -a
Options:
- -a
- Display the nodes for all interfaces.
Description:
Use the wlanctl utility to print node tables from IEEE 802.11 interfaces.
Use the -a flag to print the nodes for all interfaces, or list
one or more 802.11 interfaces to select their tables for examination.
For example, to examine the node tables for atw0, use:
wlanctl atw0
The wlanctl utility displays the node table.
For example:
atw0: mac 00:02:6f:20:f6:2e bss 02:02:6f:20:f6:2e
node flags 0001<bss>
ess <netbsd>
chan 11 freq 2462MHz flags 00a0<cck,2.4GHz>
capabilities 0022<ibss,short preamble>
beacon-interval 100 TU tsft 18425852102545544165 us
rates [1.0] 2.0 5.5 11.0
assoc-id 0 assoc-failed 0 inactivity 0s
rssi 161 txseq 10 rxseq 1420
atw0: mac 00:02:2d:2e:3c:f4 bss 02:02:6f:20:f6:2e
node flags 0000
ess <netbsd>
chan 11 freq 2462MHz flags 00a0<cck,2.4GHz>
capabilities 0002<ibss>
beacon-interval 100 TU tsft 18425852105450086784 us
rates [1.0] 2.0 5.5 11.0
assoc-id 0 assoc-failed 0 inactivity 0s
rssi 159 txseq 2 rxseq 551
atw0: mac 00:02:6f:20:f6:2e bss 02:02:6f:20:f6:2e
node flags 0000
ess <netbsd>
chan 11 freq 2462MHz flags 00a0<cck,2.4GHz>
capabilities 0022<ibss,short preamble>
beacon-interval 100 TU tsft 18425852102558548069 us
rates [1.0] 2.0 5.5 6.0 9.0 11.0 12.0 18.0 24.0 36.0 48.0 54.0
assoc-id 0 assoc-failed 0 inactivity 145s
rssi 163 txseq 9 rxseq 2563
This example is taken from a network consisting of three stations running
in ad hoc mode. The key for interpreting the node printouts follows:
- mac
- In the sample node table, the first network node has MAC number 00:02:6f:20:f6:2e.
- bss
- The first node belongs to the 802.11 network identified by
Basic Service Set Identifier (BSSID) 02:02:6f:20:f6:2e.
- node flags
- Only one node flag, bss, is presently defined.
The first node is distinguished from the rest by its node flags:
flag bss indicates that the node represents the
802.11 network that the interface has joined or created.
The MAC number for the node is the same as the MAC number for the interface.
- ess
- The name of the (Extended) Service Set we have joined.
This is the same as the network name set by
ifconfig
with the ssid option.
- chan
- The wlanctl utility prints the channel number, the center
frequency in megahertz, and the channel flags.
The channel flags indicate the frequency band ( (2.4GHz or
5GHz), modulation (cck, gfsk,
ofdm, turbo, and dynamic cck-ofdm),
and operation constraints (passive scan).
Common combinations of band and modulation are:
Band |
Modulation |
Description |
2.4GHz |
cck |
11Mb/s DSSS 802.11b |
2.4GHz |
gfsk |
1-2Mb/s FHSS 802.11 |
2.4GHz |
ofdm |
54Mb/s 802.11g |
2.4GHz |
dynamic cck-ofdm |
Mixed 802.11b/g network |
5GHz |
ofdm |
54Mb/s 802.11a |
5GHz |
turbo |
108Mb/s 802.11a |
- capabilities
- Ad hoc-mode and AP-mode 802.11 stations advertise their
capabilities in 802.11 Beacons and Probe Responses.
The wlanctl utility understands these capability flags:
Flag |
Description |
ess |
Infrastructure (access point) network |
ibss |
Ad hoc network (no access point) |
privacy |
WEP encryption |
short preamble |
Reduce 802.11b overhead |
pbcc |
22Mbps 802.11b+ |
channel agility |
Change channel for licensed services |
- beacon-interval
- In the example, beacons are sent once every 100 Time Units.
A Time Unit (TU) is 1024 microseconds (a "kilo-microsecond" or kus).
Thus 100 TU is about one tenth of a second.
- tsft
- 802.11 stations keep a Time Synchronization Function Timer (TSFT) which counts up in microseconds.
Ad hoc-mode stations synchronize time with their peers.
Infrastructure-mode stations synchronize time with their access point.
Power-saving stations wake and sleep at intervals measured
by the TSF Timer. The TSF Timer has a role in the coalescence of 802.11 ad hoc networks ("IBSS merges").
- rates
- 802.11 stations indicate the bit-rates they support, in
units of 100KB/s in 802.11 Beacons, Probe Responses, and Association Requests.
The wlanctl utility prints a station's supported
bit-rates in 1Mb/s units. A station's basic rates are flagged by an asterisk (*).
The last bit-rate at which a packet was sent to the station is enclosed by square brackets.
- assoc-id
- In an infrastructure network, the access point assigns to each
client an Association Identifier, which is used to indicate traffic for power-saving stations.
- assoc-failed
- The number of times the station tried and failed to associate with its access point.
- inactivity
- The number of seconds that elapsed since a packet was last received from the station.
When this value reaches net.link.ieee80211.maxinact, the
station is eligible to be purged from the node table.
- rssi
- Unitless Received Signal Strength Indication (RSSI).
Higher numbers indicate stronger signals.
Zero is the lowest possible RSSI.
On a hostap- or adhoc-mode interface,
the node with node flag bss set uses rssi to indicate
the signal strength for the last packet received from a station that doesn't belong to the network.
On an infrastructure-mode station, the node with node flag bss set
indicates the strength of packets from the access point.
- txseq
- The next 802.11 packet sent to this station will carry this transmit sequence number.
The 802.11 MAC uses the transmit sequence number to detect duplicate packets.
- rxseq
- The last packet received from this station carried this transmit sequence number.