CCNP Wireless CUWSS 642-732 Summary Notes 16 : Layer 2 Active Site Survey using AirMagnet Survey Pro

AirMagnet Survey

Layer 2 site survey can be performed with AirMagnet Survey PRO to determine the access point placement and coverage. AirMagnet Survey PRO has the capability of doing pre-site surveys (before the install) and post-site surveys (after the install), also known as an audit, to ensure adequate coverage.

In the configuration menu:

• Select the SSID
• Set the Tx power to match that of the AP
• Select Channel Width

Survey Modes:

• Active Survey – (Default)  the wireless network card actively associates itself with the selected access point or SSID, sending and receiving RF packets to and from the access point or SSID. If a specific AP is not selected, then the PC will connect to the AP that has the strongest signal.
• Active with Iperf for greenfield survey – Airmagnet syncs with an Iperf server to test throughput on the uplink and downlink.
  •  Watch for the following:
    • Uplink data rate
    • Downlink data rate
    • Signal strength
    • Noise
    • Signal-to-noise ratio (SNR)
    • Percentage of packets lost
    • Percentage of packets retried
  • Turn power down to at least half of what the 802.11n client supports
  • Configure the access point and client for 40-MHz wide channels to improve throughput up to 300 Mb/s. Channel bonding must be enabled on the client and
    the access point for 40-MHz high throughput.

iperf -p <port> -s <server>

• Passive – simply listens to the RF data moving through the site, detecting and recording all RF signals and noises in the environment.

When performing a site survey with AirMagnet Survey PRO, at least one active survey of each access point should be completed (two are recommended). When all active access point site surveys are completed, a passive site survey of the floor should be completed.

Pre- Installation Site Survey Procedure:

• Conduct one passive survey of the floor or facility with the SSID set to Any.
• After you have completed coverage of the floor or facility, merge the survey data.
  • Merge the survey data by access point
  • Then merge the merged access point data files
  • Finally, merge the merged access point data file with the passive survey data file.
• review the data for proper placement of additional access points to fill in any null areas.
  • Check the AP Noise level
  • AP SNR level
  • AP Speed
  • AP Retry Rate
  • Packet loss rate

Active Survey Procedure

• Choose the AP to associate to
• Specify the location of the AP to begin
• walk around the area
• save survey data

Passive Survey Procedure

• Choose passive survey and leave SSID as any
• walk around the area
• save survey data

Generate a Report

AirMagnet can generate 10 different reports:

1. Overall Coverage Report by Channel: Contains data about the overall RF signal
   coverage on the selected channel
2. Overall Coverage Report by SSID: Contains data about the overall RF signal coverage of the selected SSID
3. Overall Coverage Report by AP: Contains data about the overall RF signal coverage of the selected access point
4. Per Channel Report: Contains signal data of the selected channel
5. Per SSID Report: Contains signal data of the selected SSID
6. Per AP Report: Contains signal data of the selected access point
7. Channel Interference Report: Contains data about the channel interference
8. AP Interference Report: Contains data about the interference between the access points
9. AirWISE Report: Shows data relating to the AirWISE screen
10. Spectrum Analyzer Report: Shows reports on Spectrum Analyzer data

Survey Modes using 802.11n APs.

When surveying for 802.11n, an Iperf server is used with AirMagnet Survey PRO to measure uplink and downlink data rates.

• Greenfield mode: This means no legacy 802.11 devices. All devices are 802.11n-capable.
• Mixed mode: Mixed mode supports both legacy devices 802.11a/b/g as well as 802.11n. This mode uses both a high-throughput preamble and a legacy preamble.
• Legacy mode: Support for 802.11a/b/g clients, no 802.11n clients.

References:

1. CCNP Wireless  (642-732 CUWSS) Quick Reference Guide by Jerome Henry
2. IPexpert’s CCNP CUWSS Wireless Voice on Demand (642-731)
3. CUWSS Student Guide v1.0