Controller Based WLANs

How to lock an Air Monitor to scan only a specific channel?
Q:

How to lock an Air Monitor to scan only a specific channel? 

 



A:

Air monitors generally scan all the channel one by one with a specific time interval. For troubleshooting certain RF or Rogue detection related issues, collecting air packet captures for an AM on one channel, we may need to lock the AM to a specific channel so that the AM would continuously scan or operate on that particular channel. 

 

We can lock the Air Monitor to scan only one specific channel using the below command, 

#am scan <AM-IP-ADDRESS> <CHANNEL-NUMBER-TO-LOCK> bssid <BSSID-OF-THE-AIR-MONITOR> 


Example: 

(Rajaguru-3400) #show ap active ap-name AP-135-001

Active AP Table
---------------
Name        Group  IP Address  11g Clients  11g Ch/EIRP/MaxEIRP  11a Clients  11a Ch/EIRP/MaxEIRP  AP Type  Flags  Uptime  Outer IP
----        -----  ----------  -----------  -------------------  -----------  -------------------  -------  -----  ------  --------
AP-135-001  meow   10.0.0.6    0            AM                   0            AM                   135      Aa     7m:46s  N/A

Flags: 1 = 802.1x authenticated AP; 2 = Using IKE version 2;
       A = Enet1 in active/standby mode;  B = Battery Boost On; C = Cellular;
       D = Disconn. Extra Calls On; E = Wired AP enabled; F = AP failed 802.1x authentication;
       H = Hotspot Enabled; K = 802.11K Enabled; L = Client Balancing Enabled; M = Mesh;
       N = 802.11b protection disabled; P = PPPOE; R = Remote AP;
       S = AP connected as standby; X = Maintenance Mode;
       a = Reduce ARP packets in the air; d = Drop Mcast/Bcast On; u = Custom-Cert RAP;
       r = 802.11r Enabled

Channel followed by "*" indicates channel selected due to unsupported configured channel.
"Spectrum" followed by "^" indicates Local Spectrum Override in effect.

Num APs:1



(Rajaguru-3400) #show ap bss-table ap-name AP-135-001

fm (forward mode): T-Tunnel, S-Split, D-Decrypt Tunnel, B-Bridge (s-standard, p-persistent, b-backup, a-always)

Aruba AP BSS Table
------------------
bss                ess  port  ip        phy   type  ch/EIRP/max-EIRP  cur-cl  ap name     in-t(s)  tot-t   mtu   acl-state  acl  fm
---                ---  ----  --        ---   ----  ----------------  ------  -------     -------  -----   ---   ---------  ---  --
6c:f3:7f:b9:c1:40       N/A   10.0.0.6  g-HT  am    ?/?/?             0       AP-135-001  0        5m:51s  1500  -          1    Bs
6c:f3:7f:b9:c1:50       N/A   10.0.0.6  a-HT  am    ?/?/?             0       AP-135-001  0        5m:51s  1500  -          1    Bs

Port information is available only on 6xx controller.
Channel followed by "*" indicates channel selected due to unsupported configured channel.
"Spectrum" followed by "^" indicates Local Spectrum Override in effect.

Num APs:2
Num Associations:0

 

LOCKING THE G RADIO ON THE AM TO CHANNEL 1: 

(Rajaguru-3400) #am scan 10.0.0.6 1 bssid 6c:f3:7f:b9:c1:40

 


LOCKING THE A RADIO ON THE AM TO CHANNEL 116+: 

(Rajaguru-3400) #am scan 10.0.0.6 116+ bssid 6c:f3:7f:b9:c1:50

 

To verify that the AM is locked to a specific channel, 


Run "show ap monitor scan-info ap-name <AP-NAME>", multiple time to confirm that the "Current Channel" remains on the locked channel. 

(Rajaguru-3400) #show ap monitor scan-info ap-name AP-135-001

WIF Scanning State: wifi0: 6c:f3:7f:b9:c1:50
---------------------------------------------
Parameter                      Value
---------                      -----
Probe Type                     am
Phy Type                       80211a-HT-40
Scan Mode                      all-reg-domain
Scan Channel                   no
Disable Scanning               yes
RegDomain Scan Completed       yes
DOS Channel Count              0
Current Channel                116+
Current Scan Channel           60+
Current Channel Index          10
Current Scan Start Milli Tick  468800
Current Dwell Time             500
Current Scan Type              active

Scan-Type-Info
---------------
Info-Type          Active  Reg-domain  All-reg-domain  Rare  DOS
---------          ------  ----------  --------------  ----  ---
Dwell Times        500     250         200             100   500
Last Scan Channel  60+     161+        153+            0     0

WIF Scanning State: wifi1: 6c:f3:7f:b9:c1:40
---------------------------------------------
Parameter                      Value
---------                      -----
Probe Type                     am
Phy Type                       80211b/g-HT-40
Scan Mode                      all-reg-domain
Scan Channel                   no
Disable Scanning               yes
RegDomain Scan Completed       yes
DOS Channel Count              0
Current Channel                1
Current Scan Channel           9+
Current Channel Index          8
Current Scan Start Milli Tick  378800
Current Dwell Time             500
Current Scan Type              active

Scan-Type-Info
---------------
Info-Type          Active  Reg-domain  All-reg-domain  Rare  DOS
---------          ------  ----------  --------------  ----  ---
Dwell Times        500     250         200             100   500
Last Scan Channel  9+      2+          14              0     0

 

Run "show ap arm scan-times ap-name <AP-NAME>" multiple times to check that the "timer-tick" keeps increasing only for the locked channel. 

(Rajaguru-3400) #show ap arm scan-times ap-name AP-135-001

Channel Scan Time
-----------------
channel  assign-time(ms)  scans-attempted  scans-rejected  dos-scans  flags       timer-tick
-------  ---------------  ---------------  --------------  ---------  -----       ----------
34       200              1                0               0          D           303
36       15400            36               0               0          DVACLFETS   529
38       400              2                0               0          D           314
40       31300            74               0               0          DVACULBPTS  530
42       400              2                0               0          D           330
44       31300            74               0               0          DVACULFBTS  531
46       400              2                0               0          D           346
48       32300            76               0               0          DVACULBPTS  532
52       29300            70               0               0          DVACULETS   534
56       5300             22               0               0          DVCULBTS    507
60       31300            73               0               0          DVACULBTS   534
64       29300            70               0               0          DVACULBTS   518
100      9900             21               0               0          DAL         517
104      19800            42               0               0          DAUL        518
108      18800            40               0               0          DAUL        519
112      17800            38               0               0          DAUL        521
116      17800            38               0               0          DAUL        1129    <<<<<<<<
120      800              4                0               0          DUL         457
124      800              4                0               0          DUL         468
128      800              4                0               0          DUL         478
132      15800            34               0               0          DAUL        523
136      800              4                0               0          DUL         499
140      800              4                0               0          DUL         510
144      800              4                0               0          DUL         520
149      15150            36               0               0          DVACLFETS   526
153      31100            73               0               0          DVCULBPTS   531
157      30900            72               0               0          DVACULFBTS  531
161      29750            69               0               0          DVACULBPTS  533
165      13700            32               0               0          DVCTS       478
1        18850            44               0               0          DVACLFTS    1129    <<<<<<<< 
2        19050            45               0               0          DACLS       432
3        19300            45               0               0          DCLS        427
4        19550            46               0               0          DACLS       428
5        38100            90               0               0          DVACULPS    429
6        37100            88               0               0          DVACULTS    430
7        38100            90               0               0          DVACULFS    432
8        38100            90               0               0          DACULS      433
9        37600            89               0               0          DACULS      433
10       19050            45               0               0          DACUS       423
11       19050            45               0               0          DVACUPTS    423
12       18450            42               0               0          DACUS       425
13       19050            45               0               0          DACUS       427
14       800              4                0               0          D           429
Channel Flags: D: All-Reg-Domain Channel, C: Reg-Domain Channel, A: Activity Present
               L: Scan Secondary Above, U: Scan Secondary Below, Y: Scan 80MHz, Z: Rare Channel
               V: Valid, T: Valid 20MHZ Channel, F: Valid 40MHz Channel,  P: Valid 40MHZ Channel Pair
               E: Valid 80MHz Channel (lower 20M), B: Belongs to valid 80MHz channel
               O: DOS Channel, K: DOS 40MHz Upper, H: DOS 40MHz Lower, N: Split Channel Scan
               R: Radar detected in last 30 min, X: DFS required, S: Transmit Allowed

WIF Scanning State
-------------------
Scan mode   channel  current-scan-channel  last-dos-channel  timer-milli-tick  next-scan-milli-tick (jitter)  scans (Tot:Rej:Eff(%):Last intvl(%))
---------   -------  --------------------  ----------------  ----------------  -----------------------------  ------------------------------------
Aggressive  116+     60+                   0                 998670            37370 (-298)                   1060:0:100:100
Aggressive  1        9+                    0                 998670            37370 (-339)                   846:0:100:100

 

Version History
Revision #:
2 of 2
Last update:
3 weeks ago
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