Troubleshooting Wi-Fi client quality issues can be very frustrating, users have no idea what the details are and have no idea what to ask for. Normally you end up with a description of the problem that simply states my device <brand name here> is slow. Or your network is terrible. Beyond that it is up to you to determine what may be going on and what the issue is. Once you have narrowed the issue down to a single client the RF test tools can help you gain valuable insight into what issues may be impacting the client’s experience.  The RF test tools built into the Aruba Controller and the Instant AP can be used to test and expose different aspects of the client’s RF connection. By using the AP’s radios to send null data in a test stream the client can receive the data, then read it and acknowledge it or request a retry. The AP then reports statistics such as SNR, retry and failure rates for the test data. This information can give you insight into where to look next to solve the users problems.

 

Command structure

#rft test profile <selected profile> <select method for AP> <AP identity> <select method client> <client Identity> <modifiers>

ap-name         Test AP – by name

ip-addr           Test AP – by Ipv4 address

ip6-addr         Test AP – by IPv6 address

bssid               Test AP – by bssid of specific radio

dest-mac        Target Client – by Wireless MAC address

phy                 Physical channel band of the test – g or a

radio               Radio ID to test 0 = 5ghz 1 = 2.4 ghz

 

Show the profile information

#show rft profile <select profile>

(Home_1) #rft test profile ?

antenna-connectivity            Antenna Connectivity test profile

ht-link-quality                       HT Link quality test profile

link-quality                            Link Quality test profile

raw                                         RAW test profile

 

 

Show RFT results

#show rft result <all/trans-id> <id number>

All – most recent results

Trans-id – shows the listed trans-ID results

Show which results are stored

#show rft transactions

How to run RFT test

            When you run the rft command you run it from the enable prompt of the controller CLI or SSH console. Remember that the ‘?’ and <tab/space> complete options are your friend and can help with the proper syntax for any commands.

The RF test process is run in two stages, first you execute the command and second you view the results. You need to first select the AP you want to execute the test this can be by AP name, bssid, ip-addr or ip6-addr.

#rft test profile link-quality ?

ap-name                 Name of AP that should perform the test

bssid                  bssid of AP that should perform the test

ip-addr                 IP address of AP that should perform the test

ip6-addr               IPv6 address of AP that should perform the test

 

Next you want to select the target client this is done by the targets Wi-Fi MAC address, use the command #show user-table to see current client information.

Once you run the command remember to allow time for the test to run before attempting to view the results. Often times we get impatient and try to run the ‘show rft results’ command instantly after running the test and you get a reply that there is no available results. Just give the test a few minutes to run then try again.

#show rft result trans-id 201

RF Troubleshooting test result

——————————

No result to show

—————–

Also one thing to consider – run one test at a time, again I tend to get impatient and try to run multiple RF test back to back. This never seems to work out. Run one command and allow it to finish then run another. Unfortunately there is not a message that tells you the test finished you just need to allow time and then use the ‘show rft transactions’ command to see if the trans ID is listed

 rft test profiles explained

 antenna-connectivity

The ‘antenna-connectivity’ test sends 100 null data packets from each antenna to the selected client – the client need to be connected to the AP at the time of the test but should be able to be seen by the client. The results are simple SNR and failure rates. So what does this tell you:

First, if the target client you are testing is connected to the AP and complaining about low user experience this test can give you an idea of the basic quality of their connection (rft link-quality would be better for this)

Second, if there is a difference between the two antennas results you may be looking at a degraded antenna. For internal antennas there is little you can do but RMA the AP. However, for external antennas you will want to inspect the cables, and antennas then possibly replace and retest.

 

Profile AntennaConnectivity: Built-in profile

———————————————-

Parameter   Value

———   —–

Frame Type   Null Data

Num Packets 100

Packet Size 1500

Num Retries 0

Radio       0 (1 for AP-80-S only)

 

Profile AntennaConnectivity, TransID 1, AP 192.168.12.1, Dest bc:85:56:97:a2:14, Radio 0

—————————————————————————————–

Antenna Connectivity Test Result

——————————–

Antenna 1: Avg S/N ratio: 29   Success Rate: 80%

Antenna 2: Avg S/N ratio: 29   Success Rate: 80%

Difference:               0                   0%

Link-quality

Link quality sends 100 null data packets from all antennas to the target client just like a normal connection would. This tests the client’s ability to communicate with the AP. While technically you can run this test against target clients not connected to the AP you are testing it will not yield valuable information. The better use of this profile is to see how well the client is connected to the AP, if the successful data rates are all in the low rates and the faster rates are not returning good test numbers you may want to consider the clients environment, this could be followed with the ‘antenna-connectivity’ test to see the clients SNR. In most cases link quality is the result of signal losses or client capability.

Profile LinkQuality: Built-in profile

————————————–

Parameter   Value

———   —–

Antenna     1 and/or 2

Frame Type   Null Data

Num Packets 100 for each data-rate

Packet Size 1500

Num Retries 0

Data Rate   All rates are tried

 

        #show rft result trans-id 401

Profile LinkQuality, TransID 401, AP 192.168.12.5, Dest ac:bc:32:b3:07:d3, Radio 0, Num Packets 100

—————————————————————————————————-

Data Rate Success Rate

——— ————

6.0 Mbps   100%

9.0 Mbps   100%

12.0 Mbps   99%

18.0 Mbps 100%

24.0 Mbps   99%

36.0 Mbps 100%

48.0 Mbps 100%

54.0 Mbps 100%

 

raw

The raw test sends a block of 100 null data packets to the target client and then tracks the number that gets acknowledged and the number that are retried, it also lists the SNR of the client and which radio is used for the test. This again like the other tests can be a good way to troubleshoot and determine the quality of the clients connection to a given AP.

 

Profile RAW: Built-in profile

—————————–

Parameter   Value

———   —–

Antenna      1 and/or 2

Frame Type   Null Data

Num Packets 100

Packet Size 1500

Num Retries 3

ht-link-quality

 

        #show rft result all

Profile RAW, TransID 401, AP 192.168.12.2, Dest ac:bc:32:b3:07:d3, Radio 0

————————————————————————–

Measurement       Value

———–       —–

Total Packets     100

Tx Success         99

Tx Failure         1

Excessive Retries 0

Total Retries     0

Avg S/N ratio     41

Tx by Antenna 1   100

Tx by Antenna 2   0

 

Ht-link-quality

            HT link quality is a little more involved than the other Link quality option. HT or high throughput is the designation used to the higher data rates in 802.11n and 802.11ac Wi-Fi. To test HT data rates there are some extra settings you need to understand.

 

Profile HTLinkQuality: Built-in profile

—————————————-

Parameter   Value

———   —–

Antenna     1 and/or 2

Frame Type   Null Data

Num Packets 100 for each data-rate

Packet Size 1500

Num Retries 0

Data Rate   All rates are tried

 

The HT link quality test requires the tester to specify an mcs from 0 to 23. But what is mcs? OK ‘mcs’ stands for modulation and coding scheme, or simply the way the data is placed onto the carrier. Under 802.11n and 802.11ac the HT standards specify more efficient ways to modulate more data onto the same radio carrier. But just like packing more data density onto the same size hard drive platter leads to more opportunity for errors and thus requires a cleaner substrate, higher data rates with higher QAM versions opens the door to more data rate errors.

You also have to be aware of the HT and VHT rates supported by the AP. The commands ‘#show ap ht-rates bssid <selected bssid>’ and ‘#show ap vht-rates bssid <selected bssid>’ will show what is supported by the BSSID / radio of the AP.