ZD1200 and 4 x R600 AP's - frequent disconnects and complaints.

[adrian_feudale]

We have a client with a ZD1200 and 4 x R600 AP's.  2 x R600's on each of two floors.

Latest firmware on ZD and AP's with a Ruckus support subscription.

The ISP is 1Gbps Fibre.  It is a private company with about 150 users connected every day.  Most of them are stationary and not too many visitors jumping on the WiFi.

There have been complaints recently about poor performance, disconnects, etc.

Have looked at various things such as channel changes, background scanning, channel fly, power output, etc. but nothing has really resolved it.

The activity logs show up clean.

Where is the best place to start to diagnose & resolve this issue?

Many thanks in advance!

[david_black_594]

With only 2 APs per floor, and 2 non-contiguous floors, you're mostly concerned about neighboring networks.  You can sometimes get lucky doing 2 tests with free tools.  Test #1 - using an analyzer, stand near the first AP and see what's in the air.  Sort the list by RSSI, hottest at the top, and study the display for a few minutes and see if one channel looks better than the others.  There will be a lot of fluctuations and there will be no clear winner; just pick the one that's not quite as hot as the other two.  The networks will come and go and shift around depending on the tool you're using and it's ability to deal with stuck beacons.  Test #2 - sort by channel and count number of APs on each channel (ignore APs that are weaker than -80).  For example, suppose channel 1 had only one AP but it was at -60dBm, channel 6 had 3 APs at -65, and channel 11 had 7 APs at -72.  Assuming that the volume of traffic is roughly the same on all the neighboring APs, a good choice might be channel 1.  Although it is the strongest interferer signal strength wise, your'e only sharing the channel with that one other AP.  If you pick channel 11, the weakest RSSI, then you share the airtime with 7 other APs.  Compare the results of the two tests.  There will not be a perfect answer, just pick the channel with the fewest APs and hopefully the weakest RSSIs.  Then go to the next AP and do the same except do not re use whatever you picked for the first AP.  The problem with this free-tool approach is that you're not measuring the volume of traffic on each channel.  On the above example, suppose the one AP on channel 1 is super busy and the 7 APs on channel 11 are used very lightly.  Then a better choice might be 11.  Unless you have a tool that can analyze traffic, you may need to experiment by running a week on your first choice and then try your second choice.  If you need an analyzer to see the APs, channels, and RSSI levels, you can use WiFi Analyzer if you have an Android phone, or Metageek InSSIDer on a laptop.  If you want something that will also analyze traffic, then that will cost some money.  I use AirMagnet WiFi Analyzer, Metageek EyePA, and Metageek Chanalyzer. 

[adrian_feudale]

Whoa! Thanks David!  Now that is some great info I can use!  Fantastic! 🙂

[hyosang_choi]

Could you share support_log of one of APs?

If not permmit, confirm number of deauth packet on support log.

If there are many packet about deauth, nearby it may wips.

And  check airtime using get airtime wifi0 / get airtime wifi1.

If high, Something might be causing the interference such as wips, bluetooth, many neighbor APs and so on.

In my experience, wips was one of the causes of high airtime even without many deauth packet.

[david_black_594]

Jeronimo is right.  There is a lot of good info the AP support logs.  Seach for "athstats" and check the histograms for PHY errors and airtime stats.  Also search for "stuck beacon" and see how frequently those occur.

As for background scanning interval...  It's correct that channel changes do not occur every 20 seconds or whatever the scan interval is, and that the off channel scans don't cause disconnects, but channel changes in the 2.4 band cause problems.  Depending on the enviornment, setting to 20 seconds will cause channel changes as often as every few minutes which contributes to the chaos that never ever stops. Setting static channels is almost always the best answer. In the 5GHz band, channel changes generally aren’t an issue as long as clients support CSA (which almost all do nowadays).