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Occasional Contributor II
Posts: 33
Registered: ‎06-28-2015

Regarding SNMP query on monAPInfoCurrentChannel

Outputs from a SNMP query on monAPInfoCurrentChannel (1.3.6.1.4.1.14823.2.2.1.6.7.1.1.1.2) for the SAME ap with different clients. Why does the channel change? How to interpret this channel number?

Thank you!

 

SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 4
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 1
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 1
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 11
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 11
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 11
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 11
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 11
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 1
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 1
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 1
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 6
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 1
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client= Gauge32: 1
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 1
SNMPv2-SMI::enterprises.14823.2.2.1.6.7.1.1.1.2.ap.2.client = Gauge32: 1

Moderator
Posts: 321
Registered: ‎08-28-2009

Re: Regarding SNMP query on monAPInfoCurrentChannel

[ Edited ]

from MIB

 

  monAPInfoCurrentChannel OBJECT-TYPE
         SYNTAX       Unsigned32
         MAX-ACCESS   read-only
         STATUS       current
         DESCRIPTION
            "      Channel the monitored AP is using.            "

 

so it's the channel of the AP that is seen. i.e. it's analgous to the column "chan" in the output of "show ap monitor ap-list ap-name <>"

 

Example:

 

 

root@bt:/home/aruba/mibs/6.4.2.8# snmpwalk -v2c -c whatever -M. -mALL -O0X 192.168.1.164 monAPInfoCurrentChannel

<snip>
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: 18:64:72:93:67:f0] = Gauge32: 60
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: 18:64:72:93:67:f1] = Gauge32: 60
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: 48:f8:b3:b8:20:78] = Gauge32: 36
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: ac:a3:1e:b7:df:30] = Gauge32: 36
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: ac:a3:1e:b7:df:31] = Gauge32: 36
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: ac:a3:1e:b7:df:32] = Gauge32: 36
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: c4:a8:1d:78:20:ac] = Gauge32: 40
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: e0:3f:49:59:f1:8c] = Gauge32: 157
WLSX-MON-MIB::monAPInfoCurrentChannel[STRING: ac:a3:1e:c3:7d:f2][1][STRING: e8:de:27:74:43:a2] = Gauge32: 44
<snip>

 

some ap mac ac:a3:1e:c3:7d:f2 sees a bunch of APs, they are all on different channels of course. The actual channel of the monitoring AP is not really important - but it is very very likely there will be way more APs visible on the home channel due to higher dwell time on that channel.

 

example, lets just look at radio[1] (11a) for this AP ..... 7d:f2

 

(sg-7030) #show ap database long | include ac:a3:1e:c3:7d:f2
ap205              lab                      205      192.168.1.23  Up 8d:1h:48m:33s  2      192.168.1.165  0.0.0.0     ac:a3:1e:c3:7d:f2  CM0126348  N/A   N/A   N/A           

(sg-7030) #show ap active | include ap205                   
ap205           lab      192.168.1.23  0            AP:HT:11/6/20        1            AP:VHT:36+/9/23      205      2da    8d:1h:48m:36s  N/A


(sg-7030) #show ap monitor ap-list ap-name ap205 phy-type a

Monitored AP Table
------------------
bssid              essid             chan  ap-type      phy-type       dos      dt/mt          ut/it  encr            nstas  avg-snr  curr-snr  avg-rssi  curr-rssi  wmacs  ibss
-----              -----             ----  -------      --------       ---      -----          -----  ----            -----  -------  --------  --------  ---------  -----  ----
ac:a3:1e:b7:df:30  v1-7030-psk       36    valid        80211a-VHT-40  disable  693732/693732  0/0    wpa2-psk-aes    1      0        0         0         0          13     no
ac:a3:1e:b7:df:31  v1-7030-cp        36    valid        80211a-VHT-40  disable  693732/693732  0/0    wpa2-psk-aes    0      0        0         0         0          0      no
ac:a3:1e:b7:df:32  dot1x-vlan        36    valid        80211a-VHT-40  disable  693732/693732  0/0    wpa2-8021x-aes  0      0        0         0         0          0      no
18:64:72:93:67:f0  iap-v1-psk        60    valid        80211a-HT-40   disable  121431/2797    4/0    wpa2-psk-aes    2      29       29        65        66         2      no
e8:de:27:74:43:a2  dlink-media-1D66  44    interfering  80211a-VHT-80  disable  16923/16923    15/14  wpa-psk-tkip    0      9        10        86        85         1      no
e0:3f:49:59:f1:8c  ASUS_5G           157   interfering  80211a-HT-40   disable  13831/251      23/0   wpa2-psk-aes    0      8        8         86        87         0      no
48:f8:b3:b8:20:78  PandaMANGIS       36    interfering  80211a-VHT-80  disable  13201/13201    49/48  wpa2-psk-aes    0      6        7         89        88         2      no
18:64:72:93:67:f1  iap-cp            60    valid        80211a-HT-40   disable  4821/94        4/0    wpa2-psk-aes    0      29       29        66        66         0      no
Length:8
Total:8

 

hth

-jeff

Occasional Contributor II
Posts: 33
Registered: ‎06-28-2015

Re: Regarding SNMP query on monAPInfoCurrentChannel

So those channel numbers actually reflect a fact that the AP has been scanning and *meeting* other APs/stations at different channels?

 

Also your replies help me understand a lot, as well as brings a lot of new surfing and reading for me. Anyway, they are really helpful. Thank you. 

Moderator
Posts: 321
Registered: ‎08-28-2009

Re: Regarding SNMP query on monAPInfoCurrentChannel

[ Edited ]
nzhang27 wrote:
So those channel numbers actually reflect a fact that the AP has been scanning and *meeting* other APs/stations at different channels?

Just for clarity, when I write (and our docs say) that the AP scans, it means that it moves off channel and dwells for some period of time and passively listens. The dwell time is not configuration (it used to be) and is generally assumed to be around 80ms, such that the AP can return the it's home channel before the next beacon needs to be sent. This takes place nominally once per 10 seconds (refer ARM profile scan time setting). 

 

some caveats...

>> There is a notion of agressive scanning too - that just means that if the AP is idle it can go off channel before the 10 second expiry.

 

>> There are some cases where scanning is deferred, due to various checks such as VOIP call active, load etc, this is called "scan reject".

 

>> some channels are scanned more frequently than others, there is a notion of 'rare channels' and 'inbetween channels' etc that are scanned less frequently than say the main blocks of unii-1,2,2e,3, this is achieved using a weighting scheme:

 

(sg-7030) #show rf am-scan-profile default

AM Scanning profile "default"
-----------------------------
Parameter                                   Value
---------                                   -----
Scan Mode                                   all-reg-domain
Dwell time: Active channels                 500
Dwell time: Regulatory Domain channels      250
Dwell time: non-Regulatory Domain channels  200
Dwell time: Rare channels                   100

 

 

you can view the AP scanning behaviours using the command "show ap arm scan-times ap-name <>" -- the output is reasonably self explanatory; but if you have questions post back here.

 


Also your replies help me understand a lot, as well as brings a lot of new surfing and reading for me. Anyway, they are really helpful. Thank you.

no problem at all, glad to hear it's useful info.

 

regards

-jeff

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