Random drops on AP230

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  • Updated 10 months ago
We recently have installed AP230s in every room across several middle schools. I've been receiving reports from certain teachers that use laptop carts (30 Macbook Airs) that they are randomly losing connection during the day. 

I'm wondering what the best methods to troubleshoot this are. I'm not seeing any obvious issues with the APs in any location. I can't imagine that 30 devices pushing average amounts of data are going to overwhelm a 230.

I'm hoping someone can give me a few ideas to get started with. Thanks in advance for your time!
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Antonio Pereira

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Posted 2 years ago

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Rob Pritchard

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How are the laptops authenticating on the wireless network?  If it's RADIUS, what are the Internet connection speeds for your schools?
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Antonio Pereira

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It is WPA2-PSK authentication. 
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Gary Smith, Official Rep

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Hi Antonio,

I would set up a client monitor on one of the MacBook Air's that is reported to see an issue. If the connection drops, you will be able to see a reason for the drop in the logs. This should be your first step in investigating the issue.

Kind Regards,
Gary Smith
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Antonio Pereira

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Thank you for the advice Gary. I am new to troubleshooting Aerohive products. Any bit helps. 
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Gary Smith, Official Rep

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No problem. For light reading, check out David Coleman's blogs;
http://boundless.aerohive.com/blog/troubleshooting-wi-fi-connectivity-with-the-hivemanager-client-mo...
http://boundless.aerohive.com/blog/troubleshooting-8021xeap-connectivity-with-hivemanager-tools.html

This
gives a great insight into the Client Monitor tool and how to set it
up. The client monitor tool is also very useful in understanding roaming behaviour.
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Kevin Gee

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Antonio / all,

What version of HiveOS are you running?

Probably not the same issue, but every now and then one of my AP230s seems to stop passing traffic for clients, to fix it I have to reboot the AP.  I think this may this may have been introduced by installing HiveOS 6.6r1b.2338 - if anyone has any ideas on this please do let me know :-)

Regards, Kevin.
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Antonio Pereira

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HiveOS 6.6r1b.2338  is also the version we are running.

Can anyone confirm any problems related to this OS? Thanks. 
(Edited)
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Brian Powers, Champ

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"We recently have installed AP230s in every room across several middle schools."

EVERY Classroom?!?! :/

Did you work with a VAR to do some extensive tuning of the WLAN?  As if not, I'd imagine you have lots of channel overlap and are mucking up your RF greatly.  

With 3 non-overlapping channels in the 2.4 GHz side and upwards of 9 (if not using DFS and set for 20 MHz wide channels), your RF could be a trainwreck.  

If you're not using a custom radio profile, the default Aerohive radio profile for the 5 GHz band default to 80 MHz wide channels (which I think it a terrible idea btw Aerohive!), meaning that non-DFS you are set with 2 non-overlapping channels.

I'd start at the RF level, clean that up and see what/how that impacts your client associations if this has not or was not done during the install...

A quick "show acsp neighbor" from one of the APs would reveal a lot about what the RF in the area looks like.  A "show int wifi1" would tell us the channel width of the radio to know if its 20/40/80 MHz.  
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Antonio Pereira

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Max power on these profiles is 20 dBm. From what you are saying, it seems like they might not be able to lower themselves enough? 
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Bryan Tetlow

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I will concur on the RF planning being needed -- I took over installation that had AP roughly every 30 feet from each other and all were on max output!   When they migrated to AH, they didn't use a new location plan --- FORTUNATELY --- a survey was done and quite literally almost 1/3 of installed AP's were turned off, and most went from full power to as low as 1db.

Also note on AP230 -- BOTH bands use GAIN antenna -- normally (other brands) I have found 3db gain typical, but AH gain on these is double that, so that means, MUCH more sensitive to reception, and also very easy to have too much output available.

In the end, other than 2 specific locations, which were used for wireless bridging, and on a dedicated channel, NOTHING was left at default or uses auto for power.

Auto-channeling is another beast....

Cannot recommend strongly enough --- if there's an AP in every classroom, get a survey done asap -- old-school wireless planning does not apply anymore -- more is NOT better, neither is higher power!
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Brian Powers, Champ

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I would absolutely lower that max power setting.  In the deployments that I've done like this, we ended up with more APs statically set to 4dBM or less on the 2.4 GHz side and 7 dBM or less on the 5 GHz side.  And this still provided any needed overlap in adjacent rooms.

And to Bryan Tetlow comment, we actually turn off ~50% of the 2.4 GHz radios as well as part of the tuning process.
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Bryan Tetlow

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I wished construction and clients here would allow us to do that!  :)   Medical equipment is SO FAR behind modern technology when it comes to wireless...    We had to implement a special SSID to allow for 802.11b connections.... it's denied on all other radio setups...
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Aaron Valente

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I absolutely agree with Brian Powers.  Sometimes more is not better.  The AP's are certainly conflicting and pulling your clients one way or the other.
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Steven Wallace

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I am not an expert by any means but here are a few things I would look at. First I would see how many clients can connect to the AP230. If you are having too many on the access points it could be causing connection issues for any client over that number.

Also how close are the access points? On 2.4ghz you only have 3 channels and if you have too many close together 2 of those APs could be both on the same channel and that could cause problems. 

Also, do these clients roam at all or do they stay in each classroom? The access points are set up by the SSID for roaming but you can change the setting to where when the connection drops below a certain bandwidth it will roam to the next AP. By default it is set to go all the way down to 1mbps. So it can be to the end of the range for one AP but still within that threshold and be closer to another AP but because it has not dropped below the threshold. 

Just some ideas but I am not expert and we mainly use our APs on our dock for moving freight with hand held scanners. So we most likely see different problems then. 
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Bryan Tetlow

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We had an issue with MAC products where the devices would go to "sleep" and then never reconnect.  But if the client disabled and re-enabled the wireless, they would magically reconnect.

Is your outage is similar to this --- I can't tell by thread --- then there is a power saving option that is off by default --we found-- in our AP230's.

It ONLY affected MACS, never any other type of client....

Also, I see referenced here 802.11ac ---

Be VERY careful how you implement this if that's the case.

The band plan for 20/40/80 mhz channeling will come into play heavily if there is close proximity to AP's and their interference with each other.  The phenomenon here is also similar to what you're reporting, and in close room situation, it was found to be a rolling issue...this room down, next one not, then visa versa and rarely both at same time...

If you're using wide-channel anything in wireless, you should make use of the band-plan so you can see where your overlaps will be -- despite more bandwidth on 5ghz, once you start going wide-channels, that bandwidth disappears VERY quickly.  In some cases, you can only get 2 channels in a area without overlap....if supported, 160mhz gives... 1 channel on a plan I recently reviewed.
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Johnny Matthews

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Sorry to resurrect this old thread, but what setting was this? I am having this exact problem in some places on my network. We use Macbooks extensively and have to do the Wifi off/on trick to get them to connect after sleeping.

Is it the 'skip backgrounds scan when sleeping' setting in the radio profile? 
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Rob Pritchard

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Even though this isn't my post, I appreciate everyone's comments.  I've definitely learned a thing or two, which is the whole purpose of this community.  Since there are a lot of schools that are putting an access point in every classroom, and there can potentially be issues with overlapping channels from neighboring APs that are in range of each other, is modifying the power level of each access point the answer?  I don't think I've seen any comments on this thread yet when it comes to capacity, which is why we have put an access point in every classroom.  We will potentially have 50 or more wireless devices in every classroom within the next year or two, so removing access points, in my opinion, is not an answer to resolve issues with overlapping channels since we have a capacity need.  I know that my AP230s are currently set to handle up to 100 clients, but I really have no desire to push them to that limit.  If the clients are going to be roaming from room to room as students change classes, is it best to just lower the power level of each classroom AP so that they connect easier to the AP in the classroom they move to?  And if the power level is lower on the AP, does that prevent them from seeing so many neighboring APs?
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Nick Lowe, Official Rep

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Consider that the Wi-Fi capacity is limited by channel, NOT by the radios in APs. You will nearly always run out of channel capacity long before AP capacity.

If you have 2 radios in 2 APs and they can see each other above the CCA (Clear Channel Assessment) threshold, you have the capacity of only 1 radio in 1 AP. It is all about frequency reuse.

Wi-Fi is contention based. Adding an extra AP for more radios when there are already multiple radios in different APs on same channel does not add capacity.

Do not forget that the clients are part of the equation too, they also use a radio to transmit.
(Edited)
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Nick Lowe, Official Rep

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You need to think in terms of airtime.

An associated client that is not using much airtime is not using much of the available capacity.

An associated client that is using a lot of airtime is using a lot of the available capacity.

A client using a higher data rate will consume less airtime for a given amount of data than a client using a lower data rate.

Asking or thinking about how many clients an AP can handle is meaningless without qualification.
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Nick Lowe, Official Rep

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Yes, lowering the TX power level for a radio can help and is often appropriate, but only to a degree. It is easy to go too far and end up in the situation where we observe excessive RX error rates, causing high levels of retransmissions to occur - to which you lose airtime and capacity. You get much the same thing if you disable too many of the lower data rates.
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Bryan Tetlow

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@Rob --
I have several areas where this was a concern as well.  The solution -- split the radio into 2 unique uses.  One for 2.4ghz, the other for 5ghz.

We have a very large "auditorium (250seat)" and several large conference centers (200ea) in the mix.  In those cases we have never had any issues with hitting any hard limits with client counts.  We also have dedicated lecture hall and classrooms for education.  Even when full, we've never had any issues and I have just 2 AP's within these spaces, and 1 'overflow' outside covering overloads.

The thing we've run into --- and dual (separate) AP's answers this to a degree.... network bandwidth to AP's is still 1gb max...  
At least with the AP230's we use, trunking the connections is not available !!would be great to have that!!

All our AP's are home-run to dedicated AH switch(s), which is connected to our 10gb backbone via fiber...no copper except to AP's to get in the way of bandwidth.  Much like you might do for a VoIP setup.

The other consideration if you're worried about too many clients --- start making use of load balancing options that are in the AH system...  You can break clients out to different AP's based on bandwidth or client count.  We've not had to use either here, but it is a potential help.

The thing I ask and haven't gotten an answer.... what 'exactly' constitutes a client in as much as the 100 limit is on the AP's.  Frankly, we've not been able to get that many live clients to even test the limits, even in our extreme-use locations.  I am sure it has meaning, but perhaps, like my car, just because the speedometer only goes to 80, doesn't mean I can't go 100...
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Nick Lowe, Official Rep

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To be honest, it is not at all beneficial to have 2 Gb/s to the APs for capacity reasons. Capacity will in the real world be limited in the air long before it is on the wire with just 1 Gb/s. Outside of specific niche use cases or contrived testing, this just is not seen in the real world for the vast majority of deployments. It is much the same with Wave 2 APs for many to most use cases.

The following is a good read here... Yes, I'm linking to Ruckus' blog! :P
http://www.theruckusroom.net/2014/02/will-80211ac-stab-you-in-the-backhaul.html
(Edited)
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Kevin Gee

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Ah I see, my AP230s are connecting to HP Procurves, it's rare they have bragging rights on features :-)
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Nick Lowe, Official Rep

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For your auditorium scenario, airtime will be your limiting factor not a backhaul of 1 Gb/s.
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Bryan Tetlow

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It's always nice to enjoy things like that....   I must admit that I am surprised that AH didn't take advantage of it in one way or another.

I say this only in pure sense, as Nick noted other reasoning why this may be irrelevant  in real life when it comes to wireless like this case.
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Bryan Tetlow

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We actually never have had ANY issues with our setup...  Extreme-wireless use like auditorium or conference centers included....  I have 2 AP coverage and even am using 'ac' in them.  (Tested ac80, and it worked well, but as expected RF limited so only rarely got full bandwidth both directions.  Settled with ac40, and haven't looked back....users are VERY pleased with the offerings in those areas)
...now if I could just get rid of 2.4ghz everywhere.... I'd have it made.... :)
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Nick Lowe, Official Rep

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For those thinking of deploying or who are deploying with 1 AP per room, please read:

http://www.wlanpros.com/wp-content/uploads/2014/04/Why-One-AP-Per-Classroom-Approach-is-Wrong-.v3.pd...
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Bryan Tetlow

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That's a GREAT write-up....  It mirrors many things I've been exposed to over the years.  The mentality of more is better is a hard one diffuse though.  Even harder to resolve are those that think, just turn the power up higher.  Both have their own painful results and the battles of "good" installers and designers to get around the thinking logic is a tall order.