Radio modes on Aruba Instant

Aruba Employee
Aruba Employee

Question : Radio modes on Aruba Instant


Environment : AP modes can be changed to Environment specific to detect RF health and interference on the network.


Answer :


Radio modes on Aruba Instant


We can configure AP`s to operate in one of three modes: Access, Monitor, or Spectrum Monitor. Each mode consists of some degree of scanning functionality.


AP Scanning (Access Mode)


The primary duty of an AP is to serve clients. However, an AP also scans the air to perform these tasks:

  • Looking for better channels

  • Monitoring for Intrusion Detection System (IDS) events

  • Listening for clients

  • Searching for rogue devices

  • Participating in containment of rogue devices

By default, an AP scans its current channel in the normal course of operation and goes off channel to scan every 10 seconds. A small amount of jitter occurs to ensure that a full beacon period is examined. The AP spends 85 milliseconds scanning off-channel, that is, the AP scans the foreign channel for approximately 65 milliseconds (with 20 milliseconds of overhead used as the radio changes channels) and then reverts to its home channel.

Note:   The scanning behavior in an IAP is the same as that in a campus AP, which is to perform off-channel scanning every 10 seconds. The only difference is at boot-up: an IAP scans more aggressively (1 scan per second) during the first 10 minutes after boot-up.


AM Scanning (Monitoring Mode)


AM scanning is similar to AP scanning, except that the air monitor (AM) constantly scans other networks and does not serve clients. The AM listens, and transmits only to contain rogue APs or clients. When a rogue device must be contained, the AM can spend more time containing the rogue device than scanning, which results in more consistent enforcement. When you deploy AM`s on AP hardware that has only one radio, the AM alternates between the 2.4 and 5 GHz band on the single radio AP.


Spectrum Monitoring (Spectrum Monitor mode)


In most WLAN deployments, the primary source of any performance degradation starts at Layer 1, that is, the RF spectrum or physical layer. Aruba Instant offers integrated spectrum analysis, which adds a layer of visibility into 802.11 WLANs. Visibility into the RF allows you to see what is occurring in the air and is a key requirement for troubleshooting RF issues.

Spectrum analysis can classify and identify non-802.11 interference sources, providing real-time analysis at the point where the problem occurs. Spectrum analysis is best utilized when integrated into the WLAN infrastructure, because hand-held tools are useful only when IT staff are on-site and interference is present – an unlikely combination in distributed enterprises.

The solution to the problem is a set of integrated tools that enable visibility when using the existing infrastructure. Instant offers spectrum monitoring in two modes of operation:

  1.  Hybrid Spectrum (Background Spectrum Monitoring): An AP radio in hybrid AP mode continues to serve clients as an AP while it analyzes spectrum analysis data for the channel that the radio uses to serve clients. You can record data for both types of spectrum monitor devices. However, the recorded spectrum is not reported to the virtual controller (VC).If a non-Wi-Fi interference device is detected, a spectrum alert is sent to the VC.

  2. Dedicated Spectrum Monitor (SM): SMs are IAP radios that gather spectrum data but do not service clients Each SM scans and analyzes the spectrum band that is used by the SM radio (2.4 GHz or 5 GHz).

Note:   The main difference between Hybrid Spectrum mode and Dedicated Spectrum Monitor mode is that in Hybrid Spectrum mode, the AP reports only spectrum data for its home channel. In Dedicated Spectrum Monitor mode, spectrum data for all channels is reported.


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‎09-19-2014 05:12 AM
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HI I have a question regarding  Hybrid Spectrum mode. 


Are there any disadvantages by turning hybrid mode on.

Does it utilizes more CPU and other resources.

Does it improves client roaming


I am just wondering if i am going to achieve any benifit to clients by turning this on.


Little bit information about my setup. I have around 50 iap in same cluster with same model iAP 205. building is a library with 6 floors with single open ssid.

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