Re: Wireless NICs not obeying 'SSID' setting.

From: Sam Leffler <sam_at_errno.com>
Date: Thu, 28 Jun 2007 21:35:42 -0700
Sam Leffler wrote:
> Kevin Gerry wrote:
>> I've noticed that in a recent patch that when you set a NIC with ifconfig
>> ath0 ssid "This One" that it won't always honor that and jump on the
>> strongest one.
>>
>> Example:
>>
>> 3 WAPs: SSIDs WAP1, WAP2, WAP3
>>
>> I have set ath0's ssid to "WAP2" and ral0's ssid to "WAP3". They both will
>> honor the ssid setting for the first connection. However, after a few
>> hours/etc the drivers both associate with WAP1.
>>
>> The settings to require the specific SSID are in
>> /etc/start_if.ral0/start_if.ath0. There aren't any conflicting
>> directives to
>> force it to go blank and select a random AP.
> 
> You're probably roaming.  wlandebug roam will verify what's going on.
> You can disable roaming several ways:
> 
> ifconfig ral0 roaming device
> 
> should do the trick (if you set it to manual then you won't do what you
> want if your beacon is turned off).  Alternatively you can do
> 
> ifconfig ral0 -bgscan
> 
> as roaming won't take place w/o bg scanning.

If you are roaming you can also just fiddle with the roaming thresholds; 
   e.g. roam:rssi11g and roam:rate11g.  I haven't updated the man page 
for ifconfig for these yet; they are threshold settings that when 
crossed cause the system to consider roaming to a different ap.

The handling of ssid changed when roaming went in; it's now a "desired 
ssid".  That is, if the scan doesn't see an ap with the desired ssid 
then it'll associate to another ap if possible.  Should the ap w/ the 
desired ssid re-appear and roaming is enabled then you'll switch over to 
it.  There is also hysteresis to this algorithm so you don't just bounce 
around from one ap to another.

	Sam
Received on Fri Jun 29 2007 - 02:33:07 UTC

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