[svlug] Occasional network problem (ubuntu machine to router)

Andrew Wilcox andrew.r.wilcox at gmail.com
Wed Apr 1 11:23:39 PST 2009

Is the CPU usage abnormally high when the network problems happen?
Are you running something like beagle or something that would
intermittantly use a lot of CPU?

If this is a (very) low-end machine, that could cause packet drops.
I've seen it happen before on low-end machines that are overloaded.

Hope that helps,

On Sat, Mar 28, 2009 at 4:49 AM, Erik Steffl <steffl at tsoft.com> wrote:
> In last few days I started to get occasional (lasts 5 - 20 min or so)
> network problems between router and a ubuntu machine. The problem is
> that network performance goes sharply down, when I run ping from machine
> to router most of the packets are lost (it varies how bad it is).
> I didn't see anything suspicious in the logs, disconnecting and
> reconnecting (both software and unplugging/re-plugging the network
> cable) doesn't make any difference.
> Other computer connected to the same router works fine.
> The problem fixes itself after some time (and the network works fine).
> Any ideas how to troubleshoot this? Given that it either works or
> (almost) doesn't it seems like it's not wire problem (I don't touch the
> network cable so it seems unlikely that it would work most of the time
> but not all the time and that it would fix itself without any
> intervention). It only happens in last few days, didn't do any HW changes.
> System:
>   Ubuntu 8.10
> [   11.170407] eth1: RealTek RTL8139 at 0xb000, 00:50:ba:4d:1a:58, IRQ 18
> [   11.170414] eth1:  Identified 8139 chip type 'RTL-8139C'
> [   11.190809] 8139cp: 10/100 PCI Ethernet driver v1.3 (Mar 22, 2004)
>   Router: Netgear RangeMax WNR834B v2
>   thanks,
>        erik
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Andrew Wilcox, Lead Software Developer & Network Engineer
Wilcox Technologies, Palm Beach/Indianapolis/Lantana sites
"And, behold, there arose a great tempest in the sea, insomuch that
the ship was covered with the waves: but He was asleep.  And His
desciples came to Him and awoke him, saying, Lord, save us: we perish.
 And He saith unto them, 'Why are ye fearful, O ye of little faith?'
Then he arose, and rebuked the winds and the sea; and there was a
great calm."  Matthew 9:24-26

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