Maximum Number of Connected Wireless Users?

ryabutler · ‎03-30-2009

I was reading a wireless document that shows a design where 3 WAPs on a 802.11b/g network for 180 users.

Best practices talk about 15 to 20 users per Access Point, which is what we typically do anyway.

So, my question is can the Cisco 1230 or 1240 Access Points (as an example) support like 50 to 60 users per Access Point within range?

I understand that the WAP wireless network is a shared (like a hub) network thus bandwidth is shared among all connected wireless users.

So, understand those considerations, but I want to know if those Access Points can actually support that number of connected wireless users or if there is a maximum number of associated users?

Thank you!

jeff.kish · ‎03-30-2009

I've always heard Cisco recommend no more than 25 clients per AP. As you say, this is a bandwidth concern, but it's also a wireless overhead concern. Eventually it's not just an issue of sharing bandwidth, but an issue of how much usable bandwidth there even is.

I've seen that Cisco APs can handle quite a few more over 25, but proper design would limit it to 25. There is no hard-set limit in the AP. It will not block association requests regardless of the number of clients that are connected.

There's a configurable option to restrict clients per SSID, but there's no global client restriction that can be configured.

ryabutler · ‎03-30-2009

Thanks!

Leo Laohoo · ‎03-30-2009

I agree with Jeff. Do note that if you using a WLC/WiSM, by default there's a limit of 12.

dennischolmes · ‎03-31-2009

So this is one of those famous chicken before the egg questions. Bandwidth both on and off wire and latency are to be considered when calculating the number of users per AP. For example, if I had 50 RF Guns providing very very low requirements for bandwidth and not worrying about latency then I could have 50-60 easily. On the other hand, if this is a one to one laptop initiative in a middle school where the children may be concurrently viewing a video stream then limiting the total number to 5-9 may be more realistic. It is the application that determines your capacity. From an engineering standpoint, even with the WLC limit which is only an attempt at balancing the load, the AP ultimately has to accept the additional association requests by the 802.11 standard. I have forced over 200 associations to an AP1252 before in a lab environment. Needless to say the throughput was a joke but they did all associate.

jcosgrove · ‎09-14-2009

How do you set/view this hard limit? Is it per ap, per radio, per ssid? I am viewing some airmagnet alerts and I see alarms that say "AP association capacity full" messages and I think this may be because of a limit on an AP.

Leo Laohoo · ‎09-14-2009

According to Cisco, I haven't experience this event before, users will get the annoying messages that the AP has reached maximum user limit. However, if you continue to click on the error box, the AP will finally allow the client to authenticate after 3-5 times.

Bassist21 · ‎09-14-2009

where would you change this? We are using a Wism with 1141 model AP's.

Rob Huffman · ‎09-14-2009

Hey Guys,

There are some great references here from Leo and Steve;

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Wireless%20-%20Mobility&topic=Getting%20Started%20with%20Wireless&topicID=.ee7c7c3&fromOutline=&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.2cd27a7c

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Wireless%20-%20Mobility&topic=General&topicID=.ee6e8b8&fromOutline=&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.2cc2dd07

Hope this helps!

Rob

Lucien Avramov · ‎09-14-2009

The theoretical maximum is 2048. As part of 802.11, however, some number of

these 2k addresses are reserved bringing the IEEE maximum down to 2007.

Although the AP motherboard has memory capable of handling 2007 users, the

radio utilized in our 1200 Series AP has memory limitations which hold the

maximum number of client associations to 255.

The number of 255 is active associations, though the cam table can

contain 2048 entries because of the memory size, the number restricted

for actual active association is 255.This number is still far too large for sensible

networking but what is possible. Remember that WLAN is shared media, all users have to try

to get access to the media by waiting until it is free and then sending a request to

reserve the media for the duration of the frame size that they want to

send. If the air is busy then you have to wait a random time and start

again. So if you have too many users waiting they can end up waiting a

very long time - sort of traffic jam effect at a congested junction, one

more car and the traffic seems n times worse.I dont know as to how the number 255 was

arrived at but it is largely irrelevant as 255 is still too large to be practical for

active associations, we recommend 25-30 for most design work.

Leo Laohoo · ‎09-14-2009

Nice explanation Lucien (+5).

Lucien Avramov · ‎09-14-2009

Thanks Leo!