[clug] networking problem

Kim Holburn kim.holburn at gmail.com
Mon Sep 2 06:43:53 MDT 2013

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?

> 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.

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.

Kim Holburn
IT Network & Security Consultant
T: +61 2 61402408  M: +61 404072753
mailto:kim at holburn.net  aim://kimholburn
skype://kholburn - PGP Public Key on request 

More information about the linux mailing list