[Server-devel] Technical questions
quozl at laptop.org
Thu Jan 21 16:58:11 EST 2010
On Thu, Jan 21, 2010 at 04:18:24PM +0100, Eustace Amah wrote:
> One of the problem that am experiencing now is that I configured the
> 15 APs with same ESSID, different channels(1,6,11) shared among them
> and located all around the school. Remember that the APs are
> configured with different subnet from the lease of DHCP server but
> when more than 3 XO tries to connect it knocks everyone out
> immediately. The APs are PoE enabled. The models are Cisco Small
> Business Model WAP4410N. I have increased the power to the APs.
> Any solution to this?
There's not enough problem data above to reduce the possible causes to
something workable, but I can suggest data to capture and a way to test
for one particular problem.
Additional problem data needed:
- what does "knocks everyone out immediately" mean? Are other wireless
users losing connectivity? Do the XO laptops remain associated
(left-hand LED on)? Do the APs remain accessible through their web
interface during the symptom?
- what does "iwlist eth0 scan" show on an XO laptop? (Start Terminal,
become root, type "script scan.log", press enter, type "iwlist eth0
scan", press enter, repeat the scan a few more times, type "exit",
send me the scan.log file),
Testing for too many APs:
- turn off 12 APs leaving three running on different channels; does the
symptom still occur? You can skip this test if it is impractical.
The purpose of the test is to prevent noise in the commons.
- reduce the transmit power on all APs to the minimum value; does the
symptom still occur?
I've reviewed the WAP4410N product specifications . The XOs will be
operating 802.11g, so that is the important thing to look for in the
specifications. The WAP4410N has 2 dBi antenna, transmit power of up to
17.5 dBm, and receiver sensitivity of -73 dBm.
The specifications suggest it is an indoor unit. Check your
environment; make sure the product is not being operated below 0 degrees
C, above 40 degrees C, or above 85% humidity.
I wasn't able to find what the current firmware version is, because I've
no obligation from Cisco. You should check to see if a firmware upgrade
> -----Original Message-----
> From: Martin Langhoff [mailto:martin.langhoff at gmail.com]
> Sent: Thursday, January 21, 2010 1:09 PM
> To: James Cameron; akleider at sonic.net; Reuben K. Caron; taiwo.alabi; Eustace Amah; server-devel at lists.laptop.org; Emeka Lewis Nwankwo; kene.ijezie
> Subject: Re: [Server-devel] Technical questions
> On Thu, Jan 21, 2010 at 12:28 PM, Martin Langhoff
> <martin.langhoff at gmail.com> wrote:
> > 3 - Define how many users you can connect to an AP -- some APs have
> > "configured" hard limits in the software they ship. If you have to
> > guess, assume ~40 as the upper limit.
> Let's reword that as: assume 30, which is where most APs start having
> problems. If you are using OpenWRT, you can probably support 40. If
> you have tested your AP, then you'll know for real.
> In general, it is very hard to go over 40 active nodes per channel;
> this is mainly due to limitations of "sharing the commons" of the
> radio spectrum.
> High end APs may be able to operate different antennas in different
> channels -- so one AP acts as if it were 3, working on 1, 6 and 11.
> martin.langhoff at gmail.com
> martin at laptop.org -- School Server Architect
> - ask interesting questions
> - don't get distracted with shiny stuff - working code first
> - http://wiki.laptop.org/go/User:Martinlanghoff
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