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axe50397
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Router capacity

Mon Feb 19, 2018 1:41 am

Hi there,

I would like to know how to know/calculate the client capacity of a given router, let’s say rb951.

Let me explain. I was preparing a class with an rb951, with 60 students. No internet, 1 DHCP /25, i just needed to connect all of them on WiFi to make them download some files on an HTTP server also connected on WiFi.

The thing is that at 40 clients, the router stopped accepting clients. People (all on Windows) kept getting “impossible to connect to the wireless network”, and when some left, other could join. The CPU at the time was barely around 12%, ans with a /25, I was far from the limit.

How can I determine where was the issue and how many client an AP can handle please?
 
Paternot
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Re: Router capacity

Mon Feb 19, 2018 3:01 am

Have you checked the DHCP server leases? Does it have enough FREE addresses? With a /25 you'll have 126 usable addresses. With 60 students/class, you MAY have enough IPs to two classes in a row. Remember: the DHCP server will not reuse a given address, unless it has expired. Does the machines in the lab are always the same?
 
axe50397
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Re: Router capacity

Mon Feb 19, 2018 9:23 am

Have you checked the DHCP server leases? Does it have enough FREE addresses?
I checked the number of connected client with that. Around 37 it became harder to join, but I don’t know if it was the DHCP which wasn’t able to offer IPs, because clients wasn’t complaining about « limited connectivity » but simply « impossible to join ».

The lab was a one time lab, but I’d like to organize that more often. What can I also check please?
 
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BartoszP
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Re: Router capacity

Mon Feb 19, 2018 9:27 am

DHCP etc is not a concern.
You should check what is the WiFi speed. 60 devices connected to one AP .... expect low speeds.
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LucZWFM
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Re: Router capacity

Mon Feb 19, 2018 9:30 am

DHCP etc is not a concern.
You should check what is the WiFi speed. 60 devices connected to one AP .... expect low speeds.

His issue is that no more clients are acccpeted, not the speed. So I still would check DHCP...
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axe50397
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Re: Router capacity

Mon Feb 19, 2018 9:43 am

So I still would check DHCP...
let’s say I didn’t have enough lease, or better, let’s say I didn’t have a DHCP server at all. Why would it prevent client to join the ap? Wouldn’t they be able to join letting them configure an ip like 169...... ?
 
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LucZWFM
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Re: Router capacity

Mon Feb 19, 2018 9:58 am

So I still would check DHCP...
let’s say I didn’t have enough lease, or better, let’s say I didn’t have a DHCP server at all. Why would it prevent client to join the ap? Wouldn’t they be able to join letting them configure an ip like 169...... ?

IP's like these are giving to an interface by Windows (maybe other os's as well, I don't know) when the interface can't get an IP from DHCP.
Why a client will not connect could be different per client and OS I would think. My experience is that clients will not connect when they can
not get an IP.
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CZFan
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Re: Router capacity

Mon Feb 19, 2018 12:04 pm

Herewith the magic question: What did the debug logs say with these issues?
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axe50397
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Re: Router capacity

Mon Feb 19, 2018 6:17 pm

Herewith the magic question: What did the debug logs say with these issues?
This is the real question. But in the rush we didn't check the logs, and as they're in RAM and limited, they're already dismissed by the time.

Is there a way to simulate 60 clients and try to get the logs at that time 😅 ?
 
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BartoszP
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Re: Router capacity

Mon Feb 19, 2018 6:25 pm

A. IP Pool for DHCP too small
B. "Max station count" set to 40 in the Advanced tab of WiFi interface.
C. Set DHCP lease to much much lower time to reuse IP addresses.
D. Too much interference for all connecting devices.
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axe50397
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Re: Router capacity

Mon Feb 19, 2018 7:12 pm

A. IP Pool for DHCP too small
B. "Max station count" set to 40 in the Advanced tab of WiFi interface.
C. Set DHCP lease to much much lower time to reuse IP addresses.
D. Too much interference for all connecting devices.
Thanks a lot, I didn't know about B. But after checking, the max count is currently 2007.

A. IP Pool was /25 (Actually, 2 different DHCPs on 2 interfaces, wlan + virtual wlan, no bridge)
B. 2007
C. 3 hours, but I was monitoring the leases.
D. That, I can't know nor check.

BTW, what need to be check when one wants to support a given number of client?
 
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chechito
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Re: Router capacity

Mon Feb 19, 2018 7:34 pm

40+ client per radio on wifi == problems

is not a mikrotik issue, wifi uses contention to control medium access, and that do not escalate well with many devices

i have success with ~40 devices on a single 2.4ghz radio on rb951Ui, in very dense environments (clients very close to the ap) and no interference, without issue, but dont expect more than 10-15 mbps of total throughput

You need to diagnose better the issue, i dont think the devices cease to associate, you have to enable logging for all wireless topic and diagnose to know exactly what happen.

What You are trying to do is a high density implementation, some of the hardest variants on wifi design

You have to tune your configuration, monitor clients data-rates, monitor client signal level, monitor client ccq, monitor radio total ccq, ensure your spectrum are clear, diagnose your clients, do QoS, use client isolation, isolate your ap from another ap on the same infrastructure.
 
axe50397
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Re: Router capacity

Tue Feb 20, 2018 3:38 am

40+ client per radio on wifi == problems

...

You have to tune your configuration, monitor clients data-rates, monitor client signal level, monitor client ccq, monitor radio total ccq, ensure your spectrum are clear, diagnose your clients, do QoS, use client isolation, isolate your ap from another ap on the same infrastructure.
thank you for the advices. To tune and monitor, i’ll have to create the same conditions, and I won’t be able to do that soon.

Anyway, we’ll firstly limit participant to 20 maximum (if internet is needed). But what can you advise me to do if we want to have from 50 to 100 users on WiFi in a probably noisy environment (in a conference room in a hotel where they already have a WiFi, but we need an internal network without internet for us with out equipments and our conf)?

Should we increase the APs numbers? Should we place them in a certain way allowing users to evenly connect to one of them? Should we work with the hotel’s equipment? Other suggestions?

For the record, we worked with the hotel’s APs, the one in the conf room and we disabled they’re WiFi to put our conf and firewall, that was the conditions of our issue.

Thanks for your help and suggestion.
 
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pcunite
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Re: Router capacity

Tue Feb 20, 2018 5:07 am

I would also consider using only G/N on the 2.4Ghz radio ... as opposed to B/G/N
 
troffasky
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Re: Router capacity

Tue Feb 20, 2018 2:46 pm


Should we increase the APs numbers? Should we place them in a certain way allowing users to evenly connect to one of them? Should we work with the hotel’s equipment? Other suggestions?
Dual band AP for sure. Hopefully some clients end up on 5G radio and some on 2G. Also, high-density wifi design isn't a Mikrotik-specific issue and there's plenty of howtos and guidance about this on the internet.

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