Maximu Devices Connect - Catalyst 9120AX

[medina.manuel]

Hello Guys, 

I am looking the maximum devices that can be connected to a Catalyst 9120AX. I found two documents, in this Cisco Catalyst 9120 Access Point Deployment Guide indicaste a maximum of 500 devices , but with the

Cisco Access Point and Wireless Controller Comparison only 200 per radio, it the have 2 radios it would be a maximum of 400. 

What is correct?

Thank in advance, 

Manuel 

[Leo Laohoo]

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@medina.manuel wrote:

I found two documents, in this Cisco Catalyst 9120 Access Point Deployment Guide indicaste a maximum of 500 devices

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How many wireless clients can connect to an AP will depend on a myriad of factors: 

1. Co-Channel Interference
2. Backbone speed from the AP all the way up to the WLC (including Duplex setting)
3. What are the wireless clients doing?  E-Mails?  IM?  Browsing the net?  HD video streaming?
4. And many, many more.  

Rule-of-Thumb is 25 wireless clients to an AP.  This number goes up to, say, 35:1, if there are not a lot of traffic. 

Where I work, I see many 3702 with wireless clients between 60 to 100 and we have not received any complaints.  

[Scott Fella]

Just to add, I think the 500 is not just wifi clients but includes clients that might be IoT using zigbee or thread.  The max wireless clients supported per radio is 200, but you never ever want to get close to that.  Like what you already have seen in documentation:

The max associated clients Cisco supports on an AP is 200 per interface - 400 per AP (so maybe we could get all 400 on the same AP - but it would likely not be very efficient if they all use it at once) QOE - would not be good.

Like what Leo mentioned, there is a rule of thumb but is not set in stone.  Having 50 clients per ap or radio might work for some, but not for others.  

[JPavonM]

The rule of thumb I normally use for an standard office space to determine the maximum number of clients associated to a 802.11ac/ax radio is the contention window value.

I try to design the WLAN in an office to have 1-AP every 31 clients at most. But remember this is a non-deterministic access and it depend on the client connection algorithm behavior.

In theory, you will have as much clients connected to an AP radio as the number of backoff values are in the first contention window, so no retransmission are likely to happen, hence increasing the QoE.

For auditoriums, classrooms or environments with lot of devices or near real-time streams of any video or audio, it all depend on the QoE you expect to have.

HTH
-Jesus
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[Leo Laohoo]

@medina.manuel, @JPavonM, @Scott Fella 

Because of CSCvy08682, the answer is <15 wireless clients (max 25) per AP (910x, 911x, 912x).  

NOTE:  This restriction does not apply to Qualcomm (QCA) APs, like the 913x, 916x and 917x.

If there are >25 wireless clients, the Broadcom (BCA) APs (910x, 911x & 912x) will quickly run out of memory and crash.

Because Cisco will not be fixing this bug, it is recommended to keep the number of wireless client to <25 &/or reboot the AP daily.