Ask the Expert: Deploying and Troubleshooting Wireless Networks

[Monica Lluis]

Welcome to this Cisco Support Community Ask the Expert conversation. This is an opportunity to learn and any ask questions about how to configure and troubleshoot a wireless network with Cisco expert  Alexander De Menezes.

Ask questions from Monday February 22 to Friday March 4, 2016

Wireless networks have became pervasive in today's world. Cisco offers very strong wireless porfolio that helps business to connect to the Internet anywhere anytime. 

This session will focus on answering question regarding how to deploy a wireless network and also, the common pitfalls and issues that might happen in an installed wireless network. 

Alexander De Menezes  is a Technical Support engineer in the Cisco Technical Assistance Center in Cisco Brussels.  He is expert on any wireless products, including Wireless LAN controllers and Access Points. He also has in-depth knowledge of AAA and IBNS technologies. Alexander joined Cisco in 2007. He holds a Master in Sciences in Advanced Electronic Engineering from the University of Warwick, UK. 

Alexander  might not be able to answer each question due to the volume expected during this event. Remember that you can continue the conversation on the Getting Started with Wireless Community

Find other  https://supportforums.cisco.com/expert-corner/events.

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[Alexander De Menezes]

Hi Daniel,

How are you verifying the 70Mbps on wireless, via Iperf?

http://www.cisco.com/c/en/us/support/docs/wireless-mobility/wireless-lan-wlan/112055-tshoot-11n-speeds-00.html#topicsub1

-What is the AP model you use?

-What band 2.4/5Ghz -802.11n/802.11ac /channel bonding enabled?

http://www.cisco.com/c/en/us/support/docs/wireless/4400-series-wireless-lan-controllers/108184-config-802-11n-wlc.html

-What is your wireless client type and wireless chipset,sometimes you need to update buggy wireless clients to latest wireless driver versions?

-Do you have AP/client capable for 802.11ac?

http://www.cisco.com/c/en/us/td/docs/wireless/technology/apdeploy/8-0/Cisco_Aironet_3700AP.html#pgfId-76539

Wireless is shared medium so you need to consider some loss, and client throughput will also be affected by client distance to AP, data rates which are enabled,interference or channel utilization on AP etc.

For troubleshooting, i would first verify config as per best practices:

http://www.cisco.com/c/en/us/td/docs/wireless/technology/wlc/82463-wlc-config-best-practice.html#pgfId-380235

You can check show run-config against for some best practice config recommendations:

https://supportforums.cisco.com/document/7711/wlc-config-analyzer

Useful commands to check:

From WLC cli, we can check for RSSI and other info:
wlc>sh ap auto-rf 802.11a/b <ap-name>
wlc>sh client detail <client mac>

wlc>show 802.11a/b

From ssh/telnet to AP:
ap>debug capwap console cli
ap>show cont d0/1     ..based on if 2.4Ghz or 5Ghz radio used

ap>show cont d0/1 | i MPDU     ..for packet aggregation settings
ap>show cont d0/1 | b queue     ..for AP queues

ap>debug dot11 dx trace print rates
ap>undebug all (to disable debug)

-Alex

[Daniel Ordóñez Flores]

Hi Alexander.

Here my answers:

1.- How are you verifying the 70Mbps on wireless, via Iperf?

Nop, I do a speedtest on http://www.speedtest.net/es/

2.- What is the AP model you use?

In fact I have a Mixed equipment but, I did my test with just one AP model AIR-CAP3702E-N-K9

3.- What band 2.4/5Ghz -802.11n/802.11ac /channel bonding enabled?

5Ghz n, 40Mhz with channel bonding

4. What is your wireless client type and wireless chipset,sometimes you need to update buggy wireless clients to latest wireless driver versions?

This is for convention center and offices so we'll expect different devices and chipset, but I did the test with my macbook pro beginning of 2013.

5.- Do you have AP/client capable for 802.11ac?

Yes.

6.- Wireless is shared medium so you need to consider some loss, and client throughput will also be affected by client distance to AP, data rates which are enabled,interference or channel utilization on AP etc.

I get it, but, in this test I was at 1 meter from the AP.

7.- For troubleshooting, i would first verify config as per best practices:

I did, actually I read first this document, the network has one SSID I was the only client on it, disable low data rates, enable bonding channel, etc.

8.- You can check show run-config against for some best practice config recommendations:

I check this link but I'm using Macbook so I couldn't make work. ;(

Now I want to ask you something that can be silly, 

 I know that  Data Rate is my connection from my Macbook Pro to the AP, I checked this and I got 145Mbs, I review my MCS and I got 15.

When I did a show client detail in data rate a got m22

I’m not sure if my original question is wrong, but for the end user he doesn't care how speed is he connected the AP, when he does a speed test on the webpage he wants to get something near to 100Mbs or event the full 100Mbs.

So ist a throughput issue? speed internet issue?

Desafortunately when the user plug his j45 cable and do the test he gets 100Mbs.

I’m not sure if get between 60 and 70 is a normal result, I need to say that this is exclusive internet service for wireless network.

Thankyou in advance. 

[ajc]

Hi Daniel, I am following your question, however I do not know if the next applies to your case. Let's see what Alex has to say.

-if you use WEP or WPA/TKIP security, The 802.11n spec states that the high throughput rates can't be enabled if either of those outdated security methods are used so your throughput would go down.

[Daniel Ordóñez Flores]

Hi Abraham

I'm using WPA2 with AES and PSK

[Alexander De Menezes]

Hi Daniel,Abraham,

Thats true, there is requirement for WLAN to have either Open or WPA2 AES encryption with WMM enabled in both 802.11n &802.11ac.

Also we need to use the Iperf for throughput tests and not the internet speed test.

You can select 80Mz channel width and enable 802.11ac on the Wireless>802.11a/n/ac >high throughput section.

As per best practice, use DCA Channel list and include channels:
36-48
52-64
100-112 incase needing UNII-2 Extended,Channels 120,124,128 not allowed in the US, and severely penalized in ETSI DFS rules.
149-161

Similar config from below 5760 link also applicable for 5508:

http://www.cisco.com/c/en/us/td/docs/wireless/technology/5760_deploy/CT5760_Controller_Deployment_Guide/802_11ac_support_on_WLC5760_and_Catalyst_3850.html

http://www.cisco.com/c/en/us/td/docs/wireless/controller/8-1/configuration-guide/b_cg81/b_cg81_chapter_0101.html#d80374e855a1635

To get max benefit from 802.11ac rates, your wireless client should also be able to support  80Mhz, short guard interval (GI) and 3 spatial streams.

Current wireless clients support short GI=400ns,but not all are 3SS capable (you need to check from client vendor specs)  .Based on your available wireless client support for GI & SS,the Iperf results can then be compared to the AP model data sheet, for ex with 3700 AP (section under Data rates supported>802.11ac data rates)

http://www.cisco.com/c/en/us/products/collateral/wireless/3700-series-access-point/data_sheet_c78-729421.html

hope that helps

-Alex

[Daniel Ordóñez Flores]

Hi Alexander, Abrham

Is any way to use Iperf with Macbook pro?

[ajc]

Let me get a MacBook pro and give a try, I do not have one.

[Daniel Ordóñez Flores]

Hi Abraham, Is already working 1.- Press Command+Space and type Terminal and press enter/return key. 2.- Run in Terminal app: ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)" < /dev/null 2> /dev/null and press enter/return key. Wait for the command to finish. 3.- brew install iperf3 So Abraham , Alex How I must do the test? If both Cliente and Server are in the same wireless network, I'm really testing the internet speed? Or a need a Server beyond my WAN to test it?

[Daniel Ordóñez Flores]

Hi Alex.

I would like to make what kind of troubleshooting process I can do, I will explain my case.

When I get wired to my Switch and I do a speedtest I get 100Mbs. If i do the same with wireless conecction I get between 60 & 70 Mbps. I try with just one user in the Wlan. I have attached my APs to 3850 Switch and I have 6gb Lag Link between my Switch and WLC 5508.

Thanks!!

[Olivier Robin]

Hi Alexander,

How do you troubleshoot random AP disassociation ?

"show ap uptime" shows that association uptime differs from ap uptime:

AP03  7 days, 15 h 54 m 38 s   0 days, 06 h 46 m 57 s
AP02  1 days, 09 h 17 m 32 s   0 days, 06 h 46 m 27 s
AP09  1 days, 09 h 15 m 40 s   0 days, 02 h 22 m 00 s
AP08  1 days, 06 h 08 m 55 s   0 days, 02 h 21 m 29 s
AP01  12 days, 07 h 05 m 36 s   0 days, 01 h 11 m 40 s

The AP are not always the same.

Thanks

[Alexander De Menezes · Accepted solution]

Hi Robinoliv,

Is this for new deployed APs, since i also see AP uptime of 1 day for example for AP02/AP09/AP08.

Short AP uptime would mean AP loosing connectivity to switch port,  so example PoE issue (like Switch PoE budget issue or AP switch port flaps or unstable switch to which AP is plugged).

For Aps which have shorter "association up time" as compared to the "AP up time", that would mean the APs are loosing connectivity to the WLC and rejoining back.

In your case there are APs with both short AP uptime and differing association uptime. 

To troubleshoot this problem:

1)You may want to check on WLC release, for example on Cisco.com we see 7.6 release marked as deferred release, so you can check on release notes and have WLC moved to a latter Cisco suggested release (can be viewed from cisco.com >software downloads page).

2)If not running on deferred WLC releases and you still see the issue, then 

Check on AP event.log/show logging as it will show some info on problem event corresponding to AP uptime data.

For example from telnet/ssh to specific AP:
ap#debug capwap console cli

ap#show logging

Also you can correlate above problem occurrence timestamps to WLC data,from WLC cli:

show msglog

show traplog

3)Enable core dump on APs:

WLC command :
config ap core-dump enable <TFTP server IP> <filename> compress 

For this we will then need to make sure the AP can reach the TFTP server.So if any crash event on the AP, the core dump will be automatically sent out by AP to TFTP server.

4)If any crash event seen on AP, we can then retrieve all the relevant "event.log/crash/rcore/coredump/show tech-support" from those specific Aps "dir flash:" for the relevant timestamp of AP problem occurrence.

For example from telnet/ssh to specific AP,you can capture:
ap#debug capwap console cli

ap#show tech-support
ap#show logging

ap#dir flash:

Under AP "dir flash" only check for files which have timestamp corresponding to problem occurrence time on APs.Then to transfer any relevant files to TFPT/FTP, for example:

ap#copy flash:crash.txt tftp:

ap#copy flash:r0.rcore tftp:

Or alternatively to transfer these files via WLC method:

(Cisco Controller) >Show ap crash-file 
(Cisco Controller) >show ap core-dump <AP name>
(Cisco Controller) >config ap crash-file get-crash-data <AP name>
(Cisco Controller) >config ap crash-file get-radio-core-dump x <AP name>
(Cisco Controller) >show ap eventlog <AP name>

Should you not see any useful data from the AP "dir flash:" for problem occurrence timestamp,then do let me know, as it may need a Cisco TAC case for detailed troubleshooting.

-Alex

[Leo Laohoo]

How do you troubleshoot random AP disassociation ?

"show ap uptime" shows that association uptime differs from ap uptime:

AP03  7 days, 15 h 54 m 38 s   0 days, 06 h 46 m 57 s
AP02  1 days, 09 h 17 m 32 s   0 days, 06 h 46 m 27 s
AP09  1 days, 09 h 15 m 40 s   0 days, 02 h 22 m 00 s
AP08  1 days, 06 h 08 m 55 s   0 days, 02 h 21 m 29 s
AP01  12 days, 07 h 05 m 36 s   0 days, 01 h 11 m 40 s

The AP are not always the same.

To add to Alexander's response about investigating why the AP keeps rebooting, how about running a TDR on the switchport.

[George Stefanick]

Alex great reference material ! 

[Alexander De Menezes]

Thanks George !

[wyfy-2015]

Hi,

I have tried to put ap3702 in sniffing mode ,(CT5760 controller) ,Unfortunately i could not find any 802.11 frames in the  remote side?

Please help