Need some tips for troubleshooting 8540 wlc

[Bekzod]

H,

I am new in wireless network (whole of my life i was wired network engineer), so appreciate if anyone can share their experience.I have wlc 8540 with air-ap4800-b-k9, wlc OS version 8.10.181.4, cpu usage 0%,memory 14% ,  supported 2000 AP has only 500 AP . users on one of the remote sites complains about their wifi is dropping, that they have 1 bar only , office has 6 APs covered all space, and all of them show registered.  So its unclear why is this happening. As I understand this might be with roaming settings on the pc and/or wlc, or something with APs signal?  Can you please share step-by-steps  and instructions to troubleshoot this issue remotely on the wlc and on the user's pc ?

Thank you

[Flavio Miranda]

Hello,

   First thing to check:  Access Point power.  If clients are getting low signal it might be the AP with low power signal.

You can check this by access the WLC and running the command "show ap config 802.11a (or b) <AP name>

then scroll down to "Tx power" and see "Current TX Power level". If this value is 1, means AP is on the maximum power possible.

You can also check this on the web interface by navigating in "WIRELESS" > "RF profile" > RRM > "Maximum power level assignment

Values from -10 up to 30 being 30 the maximum.

If you APs are at maximum power level, I´d say you are done on the WLC and now you need assistance from onside support. You need someone to walk around and run a site survey and/or spectrum analyser to make sure you dont have any interferencia source on the place.

 Lastly but also very important, make sure clients  adapters is fine. If there was no laptop replacement recently with bad wireless adapter.

  I think this is a start.

[Bekzod]

i see power level for those Aps are low for dualband is level 5- 8dbm, and for 802.11a is 3 -14dbm , how to increase it and where? another question is how to check that site access points wlans which ssid they have  and do they have 2ghz or 5 ghz ?  thank you

[Flavio Miranda]

To increase you need to remove Access Point fro global mode config.

Go to WIRELESS > Access Ponits > Radios

802.11a or 802.11b or  Dual Radios

On the right hand side, there will be a small blue square with a inverted white triangule

rover the mose over it and a menu will drop down. Select configure

In  TX power level, change from Global to Custom and change the value. 1 is the maximum.

For you question about which SSID you have on the site,  you need to check on the Access Point in which group they belong.

WIRELESS >  Select one AP and go to Advanced tab.

On the AP group name you can catch the group name.

Then move to WLAN tab and under Advanced and AP groups you can find the group that AP belongs

Click on the group and you can see the SSID associated to that Group. Those AP will be advertized by the AP on the Site.

[Bekzod]

thank you

[Dustin Anderson]

One place to see the power in the GUI is Wireless/Access Points/Radios With the 4800, you will look at the A or the Dual Band section and at the right of the list will be current power levels.

How to read Cisco power levels, 1 is max power, and each level is basically half. so say it's max is 200mW, 2 is 100, 3 is 50 etc. You should expect to see it at a power of 3-4.

As for on-site, most new devices will prefer 5GHz even if it's bad signal it will stick to it. I see this at work in older buildings that have not been updated for 5GHz density. There is not a lot you can do as it's a client issue unless you want to turn off 5GHz and force 2.4, but not recomended.

[Bekzod]

I am thinking to push their laptop NIC to prefer 2.4 , just need to find if their ssid has 2.4 option. how to check it ? thank you

[Dustin Anderson]

2 things to check, on the SSID, there is a radio policy on the first page. It should be set to all, but it it's set to A it's 5 only.

Other is to make sure the 2.4 is enabled on the APs. since you said it's 4800s, look under the dual radios. you will see 2 entries, 1 is the 2.4 and one is a monitor.

[Leo Laohoo]

Most important thing to do is to go to the site and confirm/verify if the complaints are true.  Bring a smartphone, a tablet and/or a laptop.  But bring, at least, two of the above. 

Finally, wireless NIC are an integral part of wireless networking.  If their drivers are not up-to-date, then investigating anything is a waste of time.  

[JPavonM]

Also important to check here is taht AP4800 are receiving enough power to bring up all interfaces simultaneously.

Due to the fact that these APs are UPoE and need more that 30 Watt to work properly, there is also a posibility they are not receiving enough power, or they are negotiating wrong PoE capabilities. These AP model is not reliant under such scenarios and they behave weirdly, dropping connections, shuting down radios ...
Check the power budget on the switch side (if this is a Cisco switch invoke this command 'show power inline', and check for the output on AP interfaces)

[Bekzod]

Thank you all for responding. Today will troubleshoot with user on site , so far what i gather is the signal level is for one ssid is 6dbm for another ssid is 14 dbm, and both ssid have only 5ghz radio , so there is some space to improve. 

Thank you