Controller Based WLANs

How does an AP or AM age out and discard entries from its ap-list table and how is the ?ap-inactivity-timeout? parameter related?

Aruba Employee

Product and Software: This article applies to all Aruba controllers and ArubaOS 2.5.x and later.

An AP or AM constantly scans its RF surroundings and learns about other APs, whether they are Aruba APs or third-party APs. The AP or AM keeps the discovered APs in a table and classifies them as valid, interfering, and rogue APs.

 

To display this table for each AP, issue the following command:

 

ArubaOS 2.5.x:

#show am ap-list <AP_IP_Address>

 

ArubaOS 3.3.x:

#show ap monitor ap-list ip-address <AP_IP_Address>

 

Example:

(MM2400) #show ap monitor ap-list ip-addr 10.100.135.113

Monitored AP Table
------------------
bssid              essid           chan  ap-type      phy-type         mt  it avg-rssi curr-rssi  
-----              -----           ----  -------      --------         --  -- -------- ---------  
00:0b:86:a8:ee:b0  mak-wpa2-psk     153  valid        80211a       1008746  0    24      24     
00:0b:86:b6:09:90  aruba-ap           6  unsecure     80211b/g        3766  1     0      45 
00:1a:1e:96:c8:00  guest              1  interfering  80211b/g-HT-20  3769  0     0      46    
00:1a:1e:96:c8:01  ethersphere-voip   1  interfering  80211b/g-HT-20  3768  0     0      45     
00:0b:86:ca:4d:60  tac-kwh-Supra      1  interfering  80211b/g        3765  0     0      45     
00:0b:86:da:15:e0  remote-ap-spt-70  11  interfering  80211b/g        3662  0     0      31     
00:1a:1e:8f:b2:c1  ca-vab-cp-  1      1  interfering  80211b/g        2662  0     0      44     
00:0c:41:82:54:67  linksys            6  interfering  80211b/g        2285  0     0      37  

One parameter of importance related to aging out entries in the ap-list table is the "it" parameter.

 

"it" stands for idle time. This parameter is incremented by one every time the AP containing the list scans a channel and does not hear an AP that was supposed to be on that channel.

 

For example, consider the essid aruba-ap with bssid 00:0b:86:b6:09:90 found on channel 6. Every time the AP at IP address 10.100.135.113 scans channel 6 and does not hear aruba-ap, it increments the 'it' value by one. If it hears aruba-ap, 'it' is reset back to zero.

 

To understand how entries in the ap-list table are aged out, consider three cases:

1. The monitoring AP is on the same channel as the monitored AP.

2. The monitoring AP is actually an AM.

3. The monitoring AP is on a different channel than the monitored AP.

 

For cases 1 and 2, the "it" value needs to be equal to the ap-inactivity-timeout before that entry is aged out.

 

For case 3, the "it" value needs to be twice the ap-inactivity-timeout for the entry to be aged out.

 

The default value of ap-inactivity-timeout is 5 seconds (ids general-profile in ArubaOS 3.3.x), so the value of "it" needs to be at least 5 in cases 1 and 2, and 10 in case 3.

Version history
Revision #:
1 of 1
Last update:
‎07-06-2014 07:16 AM
Updated by:
 
Labels (1)
Contributors
Search Airheads
cancel
Showing results for 
Search instead for 
Did you mean: 
Is this a frequent problem?

Request an official Aruba knowledge base article to be written by our experts.