On Wed, 6 May 2015, Rod Roark wrote:
Here's a puzzle for you experienced network administrators.
My mom-in-law is in a nursing home and I wanted to set up a MagicJack
for her to save some bucks on her phone bills. The facility has Wi-Fi
with unsecured guest access where you just have to accept the terms of
use via a captive web portal.
Long story short, I set up an old netbook computer for her with Linux
Mint Debian Edition, and disabled Network Manager and configured wlan0
in /etc/network/interfaces. I also wrote a PHP script that runs every 5
minutes via cron to automate the portal login when required. It also
detects when Internet connectivity is lost and executes an ifdown and
ifup of
wlan0 in that case.
The problem: Frequent wi-fi outages, evidenced by DNS lookup failure.
Clues are:
1. They only happen during the day when lots of staff or visitors are
around. The exception is shortly before midnight every night, which I
figure is by design.
2. They occur at random times, about 6 times per day. Thus clearly not
an intentional timeout.
3. They are cured by the ifdown/ifup cycle. If that doesn't happen then
the connection stays lost. Doing it fixes the problem every time. Thus
it has nothing to do with maxing out bandwidth.
4. The netbook is always assigned the same IP address by DHCP. Thus it
can't be IP address conflict (DHCP server misconfiguration).
5. It appears there are multiple access points in the facility with the
same SSID.
The only possible causes I can come up with are:
(a) Someone is rebooting access points when they think that might fix
something. This seems somewhat unlikely because it's also happening on
weekends when administrative staff are not around.
(b) Access point malfunction under heavy use.
Any other ideas?
I've seen this sort of problem a lot of places, even at CalEPA where I
work. I don't know why this happens, and it can waste a lot of time. I
programmed my own Linksys routers with OpenWRT so they aren't
representative, but I found that they would sometimes go offline when
traffic was heavy and require manual reboot. So I wonder if whether your
wifi router is rebooting could be tested by seeing if two connections to
it would be lost at the same time?
- Chris
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