[clug] networking problem

Duncan Roe duncan_roe at acslink.net.au
Fri Sep 6 18:27:38 MDT 2013

On Mon, Sep 02, 2013 at 10:43:53PM +1000, Kim Holburn wrote:
> On 2013/Sep/02, at 9:27 PM, Adrian wrote:
> > I have an unmanaged switch with 34 of the 48 ports connected to PCs or
> > printers in a classroom. There is an uplink  to a smaller managed
> > switch. The PCs for, good or bad, use windows xp or 7, a mix. The switch
> > after a few days of good operation then fails to pass traffic. The LEDs
> > on each port flash indicating that there is traffic on the ports or
> > attempting to send and receive traffic.
> >
> > Assuming that the switch is not at fault,
> It does rather seem that the switch is at fault.  Does the switch run
> hot when it fails? Can you borrow a similar switch and try it as a
> replacement for a few days?  Is the room dusty?  Can you take the switch
> to a compressor and blow dust out?

Agree that. My switch at home occasionally stops passing traffic. It does this
when there is little or no traffic. I've always assumed it's a firmware bug.

> > what external to the switch conditions are likely to block the switch from
> > passing traffic?
> If you disconnect the classroom uplink does the situation change?
> If you monitor the uplink do you see a lot of traffic?
> > If I re-power the switch it will work again for a few more days.

Yes that's exactly what I have to do.

Cheers ... Duncan.
> When the problem occurs, can you try disconnecting some machines and see
> if it changes anything?  Try a binary chop: disconnect half and see if
> the other half work OK.  Reconnect them and disconnect the other half.
> If one half has a problem disconnect half of that half (a quarter) etc.
> Maybe there is one machine doing something.  Or a few or maybe none.
> > If I listen with wireshark on a port what types of traffic should I look for
> > that are likely to be problematic.
> Use gkrellm and look at the volume of traffic.
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