High Collision / Poor WiFi performance

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  • Question
  • Updated 2 years ago
Hi all,

I'm aware there are several threads on the above. I have run through some basic troubleshooting and attached the results. Just need some next step advise.

A site with 83 AP330s deployed in a school campus configuration (1 AP per classroom generally)

Around 800 devices connected at any one time.

3 SSIDs broadcast on the 2.4 & 5ghz bands. 4 SSIDs in some places

Steps taken thus far to resolve issue

1. Disabled lower rates
2. Enforced 5ghz band steering
3. Lowered tx power rates
4. Disabled .11b

Here is the output of a problematic AP

"show acsp"
"show acsp nei"
"show acsp channel-info detail | inc channel"

2015-08-11 10:53:06 alert   kernel: [screen]: wifi0.2 UDP flood attack from 5cf9                                                                                                                                                              :3807:ff57(10.0.24.10) is detected. The packets will be dropped for 1 seconds.

M11#show acsp

Interface Channel select state  Channel  Power ctrl state      Tx power(dbm)
--------- --------------------- -------- --------------------- -------------
Wifi0     Enable                11       Enable                12
Wifi1     Enable                36       Enable                17

M11#show acsp nei
wifi0(7) ACSP neighbor list:
Bssid               Mode     Ssid/Hive           Chan  Rssi(dBm)  Aerohive AP  C                                                                                                                                                              U CRC STA Channel-width
e01c:417c:6e94      Access   SSID_BYOD           11    -84         yes                                                                                                                                                                        78 0   1   20
e01c:417c:6e97      Access   SSID_Enterprise     11    -84         yes                                                                                                                                                                        63 0   1   20
e01c:417a:2617      Access   SSID_Enterprise     11    -81         yes                                                                                                                                                                        41 0   2   20
e01c:417a:2614      Access   SSID_BYOD           11    -82         yes                                                                                                                                                                        35 0   1   20
e01c:417a:2616      Access   SSID_Device         11    -81         yes                                                                                                                                                                        37 0   1   20
e01c:417c:6e96      Access   SSID_Device         11    -84         yes                                                                                                                                                                        24 0   0   20
e01c:417c:6854      Access   SSID_BYOD           11    -83         yes                                                                                                                                                                        21 0   6   20
e01c:417c:6857      Access   SSID_Enterprise     11    -82         yes                                                                                                                                                                        20 0   6   20
e01c:417c:6856      Access   SSID_Device         11    -83         yes                                                                                                                                                                        24 0   8   20
e01c:417a:2594      Access   SSID_BYOD           1     -52         yes                                                                                                                                                                        28 0   9   20
e01c:417a:2596      Access   SSID_Device         1     -52         yes          28 0   9   20
e01c:417a:2414      Access   SSID_BYOD           6     -71         yes          21 0   4   20
e01c:417a:2416      Access   SSID_Device         6     -71         yes          21 0   4   20
9c5d:12cc:9894      Access   SSID_BYOD           13    -72         yes          26 0   0   20
9c5d:12cc:9896      Access   SSID_Device         13    -70         yes          26 0   0   20
e01c:417c:6f54      Access   SSID_BYOD           6     -80         yes          34 0   6   20
e01c:417c:6f56      Access   SSID_Device         6     -77         yes          35 0   6   20
e01c:417a:2597      Access   SSID_Enterprise     1     -52         yes          28 0   9   20
e01c:417c:6a14      Access   SSID_BYOD           11    -83         yes          60 6   3   20
e01c:41e3:4574      Access   SSID_BYOD           11    -85         yes          13 0   0   20
e01c:41e3:4576      Access   SSID_Device         11    -80         yes          20 0   1   20
e01c:41e3:4577      Access   SSID_Enterprise     11    -80         yes          21 0   1   20
e01c:417a:2494      Access   SSID_BYOD           11    -88         yes          38 1   1   20
9c5d:12cc:9897      Access                       13    -72         yes          6  0   0   20
e01c:417c:6e95      Access   Daily_Passcode      11    -85         yes          21 0   0   20
9c5d:12cc:9895      Access   Daily_Passcode      13    -72         yes          26 0   0   20
e01c:41e3:4575      Access   Daily_Passcode      11    -81         yes          21 0   1   20
e01c:417a:2615      Access   Daily_Passcode      11    -81         yes          35 0   1   20
e01c:417c:6855      Access   Daily_Passcode      11    -83         yes          20 0   6   20
e01c:417a:2595      Access   Daily_Passcode      1     -53         yes          28 0   9   20
e01c:417c:6815      Access   Daily_Passcode      1     -79         yes          24 0   5   20
e01c:417a:2415      Access   Daily_Passcode      6     -71         yes          21 0   4   20
e01c:417a:1b94      Access   SSID_BYOD           6     -81         yes          10 0   0   20
e01c:417c:6956      Access   SSID_Device         1     -81         yes          32 1   0   20
e01c:417c:6f55      Access   Daily_Passcode      6     -78         yes          34 0   6   20
e01c:417a:2496      Access   SSID_Device         11    -83         yes          14 0   2   20
e01c:417a:2495      Access   Daily_Passcode      11    -82         yes          14 0   2   20
e01c:417c:6a16      Access   SSID_Device         11    -83         yes          57 5   4   20
96d8:5918:01d1      Access   DIRECT-             11    -74         no           -- --  --  20
ba5a:73c3:49c6      Access   DIRECT-             1     -54         no           -- --  --  20
e01c:417c:69d6      Access   SSID_Device         6     -81         yes          40 0   1   20
e01c:417c:6816      Access   SSID_Device         1     -75         yes          28 0   5   20
e01c:417c:6817      Access                       1     -80         yes          33 0   5   20
e01c:417a:2417      Access                       6     -72         yes          21 0   4   20
e01c:417c:69d4      Access   SSID_BYOD           6     -80         yes          38 0   1   20
e01c:417c:69d5      Access   Daily_Passcode      6     -82         yes          38 0   1   20
e01c:417c:69d7      Access                       6     -81         yes          38 0   1   20
e01c:417c:6814      Access   SSID_BYOD           1     -83         yes          36 0   5   20
e01c:417c:6a54      Access   SSID_BYOD           6     -80         yes          20 0   8   20
e01c:417c:6a56      Access   SSID_Device         6     -80         yes          20 0   8   20
84c9:b2c1:2d7c      Access   ARTSFORHEALTH       6     -88         no           -- --  --  20
d890:e863:2510      Access                       11    -82         no           -- --  --  20
6676:ba16:57ef      Access   Georgia's iPhone    11    -72         no           -- --  --  20
e01c:41e3:45b4      Access   SSID_BYOD           11    -91         yes          35 0   7   20
e01c:41e3:45b5      Access   Daily_Passcode      11    -87         yes          35 0   7   20
e01c:417c:6d95      Access   Daily_Passcode      11    -90         yes          21 0   6   20


wifi1(8) ACSP neighbor list:
Bssid               Mode     Ssid/Hive           Chan  Rssi(dBm)  Aerohive AP  CU CRC STA Channel-width
9c5d:12cc:98a4      Access                       36    -78         yes          44 0   0   20
9c5d:12cc:98a6      Access                       36    -78         yes          44 0   0   20
9c5d:12cc:98a5      Access                       36    -77         yes          44 0   0   20
e01c:417c:6a28      Access   SSID_BYOD           36    -88         yes          3  0   2   20
e01c:417c:68a8      Access   SSID_BYOD           36    -88         yes          24 0   10  20
9c5d:12cc:98a7      Access   Daily_Passcode      36    -79         yes          51 0   2   40+
e01c:417c:6a2b      Access   Daily_Passcode      36    -88         yes          17 0   9   20
e01c:417c:68ab      Access   Daily_Passcode      36    -88         yes          4  0   5   20
e01c:417c:6a68      Access   SSID_BYOD           40    -83         yes          9  0   8   20
e01c:417c:6a6b      Access   Daily_Passcode      40    -83         yes          9  0   8   20
e01c:417a:2428      Access   SSID_BYOD           149   -72         yes          9  0   8   20
e01c:417a:2429      Access   SSID_Device         149   -72         yes          9  0   8   20
e01c:417a:242b      Access   Daily_Passcode      149   -72         yes          9  0   8   20
e01c:417a:242a      Access                       149   -72         yes          9  0   8   20
e01c:417c:6ea8      Access   SSID_BYOD           165   -87         yes          7  0   5   20
e01c:417c:69eb      Access   Daily_Passcode      165   -88         yes          10 0   1   20
e01c:417a:25a8      Access   SSID_BYOD           165   -56         yes          6  0   1   20
e01c:417a:25a9      Access   SSID_Device         165   -56         yes          6  0   1   20
e01c:417a:25aa      Access                       165   -56         yes          6  0   1   20
e01c:417a:25ab      Access   Daily_Passcode      165   -56         yes          6  0   1   20
e01c:417c:682b      Access   Daily_Passcode      44    -84         yes          11 0   15  20
e01c:417c:6828      Access   SSID_BYOD           44    -84         yes          11 0   15  20
e01c:417c:6d2b      Access   Daily_Passcode      48    -86         yes          2  0   1   20
e01c:417a:2628      Access   SSID_BYOD           48    -83         yes          10 0   12  20
e01c:417a:262b      Access   Daily_Passcode      48    -84         yes          10 0   12  20
e01c:417c:6eab      Access   Daily_Passcode      165   -86         yes          7  0   5   20
e01c:417c:69e8      Access   SSID_BYOD           165   -87         yes          12 0   1   20
e01c:417a:24ab      Access   Daily_Passcode      161   -88         yes          9  0   4   20
e01c:417c:6d28      Access   SSID_BYOD           48    -87         yes          2  0   1   20
e01c:41e3:458b      Access   Daily_Passcode      48    -86         yes          4  0   4   20
e01c:417a:2668      Access   SSID_BYOD           40    -88         yes          14 0   14  20
e01c:417a:15a8      Access   SSID_BYOD           44    -86         yes          5  0   2   20
e01c:417c:6968      Access   SSID_BYOD           165   -81         yes          5  0   1   20
e01c:417c:6f68      Access   SSID_BYOD           40    -86         yes          8  0   6   20
e01c:417c:6f6b      Access   Daily_Passcode      40    -87         yes          7  0   5   20
e01c:41e3:4588      Access   SSID_BYOD           48    -86         yes          3  0   2   20
e01c:417a:1bab      Access   Daily_Passcode      157   -88         yes          10 0   8   20
e01c:417a:266b      Access   Daily_Passcode      40    -87         yes          25 0   15  20
e01c:417a:15ab      Access   Daily_Passcode      44    -86         yes          4  0   2   20

M11#show acsp channel-info detail | inc channel
CU=channel utilization; TxU=Tx utilization; IU=interference utilization
Lowest cost channel: 11, lowest-cost: 44
Scanned channels: 13
Interference alert triggered channel re-evaluation: 0
Channel 1 Cost:46
                Channel deduction: 6 (CU: 37%, TxU: 2%, IU: 2%, CRC: 0%)
                Penalty on channel: 91
                Wide channel penalty: 91
        Overlapping channel adjustments: 0
Channel 2 Cost:32767
                Channel deduction: 6 (CU: 37%, TxU: 2%, IU: 1%, CRC: 1%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 3 Cost:32767
                Channel deduction: 4 (CU: 29%, TxU: 2%, IU: 2%, CRC: 0%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 4 Cost:32767
                Channel deduction: 4 (CU: 28%, TxU: 2%, IU: 2%, CRC: 1%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 5 Cost:32767
                Channel deduction: 6 (CU: 30%, TxU: 2%, IU: 1%, CRC: 1%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 6 Cost:66
                Channel deduction: 6 (CU: 37%, TxU: 2%, IU: 1%, CRC: 0%)
                Penalty on channel: 141
                Wide channel penalty: 141
        Overlapping channel adjustments: 0
Channel 7 Cost:32767
                Channel deduction: 6 (CU: 32%, TxU: 2%, IU: 0%, CRC: 1%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 8 Cost:32767
                Channel deduction: 4 (CU: 21%, TxU: 2%, IU: 3%, CRC: 1%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 9 Cost:32767
                Channel deduction: 4 (CU: 27%, TxU: 2%, IU: 2%, CRC: 0%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 10 Cost:32767
                Channel deduction: 6 (CU: 33%, TxU: 2%, IU: 1%, CRC: 2%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 11 Cost:44
                Channel deduction: 8 (CU: 42%, TxU: 2%, IU: 2%, CRC: 0%)
                Penalty on channel: 91
                Wide channel penalty: 91
        Overlapping channel adjustments: 0
Channel 12 Cost:32767
                Channel deduction: 4 (CU: 28%, TxU: 3%, IU: 0%, CRC: 2%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 40
Channel 13 Cost:32767
                Channel deduction: 2 (using history data)
                Penalty on channel: 14
                Wide channel penalty: 14
        Overlapping channel adjustments: 40
Lowest cost channel: 36, lowest-cost: 0
Scanned channels: 9
Interference alert triggered channel re-evaluation: 0
Channel 36 Cost:0
                Channel deduction: 0 (CU: 2%, TxU: 0%, IU: 0%, CRC: 0%)
                Penalty on channel: 0
                Wide channel penalty: 0
        Overlapping channel adjustments: 0
Channel 40 Cost:13
                Channel deduction: 0 (CU: 1%, TxU: 0%, IU: 0%, CRC: 0%)
                Penalty on channel: 9
                Wide channel penalty: 9
        Overlapping channel adjustments: 0
Channel 44 Cost:11
                Channel deduction: 0 (CU: 1%, TxU: 0%, IU: 1%, CRC: 0%)
                Penalty on channel: 8
                Wide channel penalty: 8
        Overlapping channel adjustments: 0
Channel 48 Cost:13
                Channel deduction: 0 (CU: 0%, TxU: 0%, IU: 0%, CRC: 0%)
                Penalty on channel: 9
                Wide channel penalty: 9
        Overlapping channel adjustments: 0
Channel 149 Cost:4
                Channel deduction: 0 (CU: 0%, TxU: 0%, IU: 0%, CRC: 0%)
                Penalty on channel: 12
                Wide channel penalty: 12
        Overlapping channel adjustments: 0
Channel 153 Cost:35
                Channel deduction: 8 (CU: 42%, TxU: 0%, IU: 0%, CRC: 0%)
                Penalty on channel: 40
                Wide channel penalty: 40
        Overlapping channel adjustments: 0
Channel 157 Cost:1
                Channel deduction: 0 (CU: 0%, TxU: 0%, IU: 0%, CRC: 0%)
                Penalty on channel: 4
                Wide channel penalty: 4
        Overlapping channel adjustments: 0
Channel 161 Cost:22
                Channel deduction: 0 (CU: 2%, TxU: 0%, IU: 0%, CRC: 0%)
                Penalty on channel: 23
                Wide channel penalty: 23
        Overlapping channel adjustments: 0
Channel 165 Cost:13
                Channel deduction: 0 (CU: 0%, TxU: 0%, IU: 0%, CRC: 0%)
                Penalty on channel: 11
                Wide channel penalty: 11
        Overlapping channel adjustments: 0
M11#



I just noticed that udp flood attack at the top .. I will check broadcast traffic on the network.

I have also attached a picture of a 1 hr interval with troubleshooting metrics of top 10 APs


Any help appreciated!
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Leith

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Posted 3 years ago

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Nick Lowe, Official Rep

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Just commenting quickly on my phone, sorry for the short reply therefore.

Have you read through and digested: http://www.wlanpros.com/wp-content/uploads/2014/04/Why-One-AP-Per-Classroom-Approach-is-Wrong-.v3.pd...
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Crowdie, Champ

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Keith Parson's document hits the nail on the head.  You always have to think about channel utilisation when deploying a high density network and just saying "one access point per class is OK" is just not good enough.
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Gary Smith, Official Rep

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Hi Leith,

I am going to assume that the issue is mainly seen on the 2.4GHz radios based on the outputs shown above.

Can you give a little more detail about the physical deployment please;
- How far apart are the AP's from eachother?
- How are the AP's mounted (ceiling or wall)?
- Can you run spectrum analysis and post the outputs?
- What are the current data rates

You mention 1 AP per classroom. The current power setting may still be too high if the AP's are too close to eachother. Based on the AP neighbour relationships I see in the "show acsp nei" output, you may want to lower the power even further.

Kind Regards,
Gary Smith
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Luke Harris

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Hi Leith,

I would also tend to echo the above, I had to deal a similar issue when my organisation initially deployed a number of APs on one of our teaching floors. Again, the 'one AP per room' approach was adopted. The motive again for this was volume/number of supported devices.

Nevertheless reducing the number of AP's and properly planning their placement, along with implementing other techniques such as spectrum analysis and ACSP...the Wi-Fi has never been better.
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Arison Mercado

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Hi, I've been dealing with the same problem for over a year with the same setup. It is still a work in progress but it's getting better little at a time. I would suggest to turning off the 2.4 Ghz in every other room and drop the dBm power settings as well. Personally in my power settings I have 2.4ghz set to 1 and 5ghz set to 5, and I have over a 100 more AP's in my high school. Once that is complete do a "Show Acsp neighbor" and make sure the SSID's are coming back to you -70 and lower, nothing higher (For example -60, -50 etc). In addition, decreasing the number of SSID worked well as well, I went from having 6 SSID's to 3 and that helped with reducing interference. 
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Arison Mercado

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Luke, 

Any luck with your WiFi network? I have reduce my 2.4 interference a lot recently but my new issue is that rooms with 2.4 shut off, clients (brand new devices) have trouble connecting to the 5 ghz and in some cases if they do connect, they show wireless connectivity but no network communication. I've pretty much exhausted my ideas on troubleshooting and i'm at a lost.
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Arison Mercado

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unfortunately all of them, Lenovo, MBP's, and chromebooks 
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Luke Harris

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Are these devices actually in range of  the other access point that is broadcasting the 2.4GHz SSID? Trying to get a feel for your topology. 
(Edited)
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Arison Mercado

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Yes, my school has a deployment scope of 1 AP per classroom with every other AP having to have 2.4 ghz turned off. So coverage is not a problem at all, its just weird that some devices will refuse to connect when the 2.4 GHz is turned off in their room but available throughout the entire building. 
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Luke Harris

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Have you tried using client monitor to see where in the connection/authentication process you are having problems? 
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Aaron Valente

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I agree. Tools>Clientmonitor and enter in a specific MAC address to get specific errors.  Then I think your problems will become more clear.
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Crowdie, Champ

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Which troubleshooting tools are you using?
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Gary Babin

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Another school district here in a similar density environment. We found it helpful to shut off 2.4 ghz on basically every other AP (and across hallways).
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Aaron Valente

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Even with half of them at 2.4 ghz shut off I would still manually assign the 1,6,11 channels to ensure less CCC. After that, you can up your power to allow better connection and lower refresh/retry (which is also going to slow everyone down).  Also, try using band-steering on your 2.4ghz to urge those devices which can, to connect to the 5ghz leaving the 2.4 less congested?