WiFi intermittently drop and not able to join Problem

[Keith_Li]

Dear All,

               I'm having below wifi disconnected issue and now has to spread to 5 sites now and its very very critical, any help would be apprecaited 

Symptom below during these day

1. error show "Unable to connect SSID"

2. Asking enter credential for connecting SSID (entered before)

3. Loading long without success connect the SSID

4. SSID not shown suddenly

5, its mostly occur on android &IOS devices, rarely happen on window laptop

Things that have done

• Manual change 2.4Ghz channel to 10 from 1, 6 & 11
• Create new network profile and move 1 x AP to the new create profile and rename the SSID to test  
• Turn off the AP "HK-YL-SRV-AP-GF-WJF, "HK-YL-SRV-AP-GF-RTJ" ,"HK-YL-SRV-AP-GF-NV7" & "HK-YL-SRV-AP-GF-36K" and connect the ssid broadcast with other APs,

It only affected the circled area, the rest location are good

Keith

[GIdenJoe]

It is very important if you are using the 2.4 GHz band that you DO NOT DEVIATE from the 1,6,11 scheme.  The problem with 2.4 GHz defined channels is that they are only 5MHz apart and 1 OFDM transmission is 20 MHz wide in the 2.4 GHz band.  That means  you are causing adjacent channel interference which is very bad.

First you'll have to make sure your deployment is fixed on one band.  So if your deployment of that SSID and system is only supposed to work on 2.4 GHz then don't transmit the SSID on the other bands so you avoid interband roaming.  And conversely if your deployment is made to work on 5 GHz try to only transmit that SSID on 5 GHz.

Then you can start your troubleshooting process.
- Check RF:  do you have enough coverage, are you using RX-SOP that is too aggressive, do you have an active interferer at that location?  You can try to check the dashboard RF page for first checks before sending someone onsite with a measurement device like a sidekick or an offering from another vendor.
- Check rogue AP's: do you happen to have another AP system that is sending the same SSID in the air with perhaps a different setting?  Check dashboard on the air marshall page.

- Check logging in Meraki dashboard, could be an indication (roaming analytics, time, DHCP and DNS log.
- Check that all AP's in that area have the same switchport config and all VLAN's are available at that switch.
- Last resort: over the air packet captures to see what is going on.

[Keith_Li]

Hi GldenJoe, 

                  I think i have solved the issue, and i checked that RF spectrum both 2.4GHz & 5GHz did not utilize the channel much & i have set RX-SOP with -65 dBM i think it is too aggressive, but in the past with this setting is working very smooth, and i have disabled the RX-SOP for both indoor　ａｎｄ outdoor AP, after 15 mins test its seem working probably

[Keith_Li]

but i experienced that the speed is slower than before, now its has around 5x Mbps whereas 100 Mbps before, any idea ?

[GIdenJoe]

In that case you should be checking the PHY rates on your endpoints if their datarate is high enough.
And you should also check the airtime utilization on the channels of said AP's.

You could have the scenario where there are simply to few AP's at that location and by removing the RX-SOP you effectively allowed the clients to remain on an AP at a lower datarate.

Other possibility is that the AP now hears more interfering signals from other sources on the same channel and is delaying it's transmissions.

In the first case you could just check using the clients.

In the second case you may need to have a small survey at location with correct gear.  But start with checking dashboard if you see any interference on the AP's.

[Keith_Li]

before disabling the RX-SOP the speed is also slow, and the other site without these issue with RX-SOP enabled and the speed is fast, i dont understand 

[Keith_Li]

i was thinking not to completey disable the RX-SOP, but to configure to -75dBm instead, what do you think ? 

[GIdenJoe]

You can ofcourse tweak it if you really have a noisy environment.  But you ought to have to check what exactly is going wrong.  Is it a coverage issue or is it a airtime/interference problem.
RX-SOP is a tool meant to be used in busy environments like office buildings with multiple customers on every floor or high density areas.

Usually when RX-SOP is used the values are around -82 up to -75 dBm.  Going higher than -75 dBm will not give any more advantages while even worsening the situation.

So yes you can play with it but I would urge you to actually go and check what exactly is going on.