Greetings Martin, I agree with Shawn that the problem requires some grunt work. Start off with a visual inspection of the network. Who knows if the installer stapled the cat5 cable somewhere or if it was punctured by a ceiling tile stringer?
-- Virtually, Tom W On 9/6/07, Gustin Johnson <[EMAIL PROTECTED]> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Almost sounds like there is a loop somwehere. The MDI MDIX does not worry > me all that much. > > How many machines and switches/routers are we talking about? > > I have also tracked down some weird TCP window scaling scaling issues this > year. If the problem is limited to certain hosts (Vista or recent linux > kernels), then perhaps: > sysctl -w net.ipv4.tcp_window_scaling=0 > > I would also leave mtr running for an hour or two and see what it records. > > Cheers, > > > > On Thu, 6 Sep 2007, Martin Glazer wrote: > > > Date: Thu, 06 Sep 2007 04:01:07 -0600 > > From: Martin Glazer <[EMAIL PROTECTED]> > > Reply-To: CLUG General <[email protected]> > > To: CLUG General <[email protected]> > > Subject: Re: [clug-talk] OT: Network Tester > > > > Shawn and Gustin, thanks for the suggestions - I will take a look at > > netem. I did look use iperf and a few other tools like nuttcp and > > thrulay but couldn't reproduce the problem or get the network to fail. > > > > The issue I am trying to troubleshoot is intermittent and random (the > > best kind!). I have so far managed to use tcpdump to capture the > > problem, but htis doesn't tell me what is causing it. I need ot get to > > the layers further down the model - Frame and Physical. > > > > I certainly cannot afford to buy one of those handy dandy network > > monitoring and testing tools, but I would be prepared to rent one or pay > > someone to test for me. > > > > On a related note - I didn't install the physical cabling and noticed on > > the managed switch that some of the ports are set to MDI and some others > > to MDIX - does anyone think that this could be an issue - I wouldn't > > think so as the switch is sensing the configuration, but you never know... > > > > Thanks > > > > Martin > > > > Gustin Johnson wrote: > >> -----BEGIN PGP SIGNED MESSAGE----- > >> Hash: SHA1 > >> > >> Since you have a linux network I would look into iperf, which should be > >> packaged in most major distros. mtr can be handy for locating problem > >> links. > >> > >> On a related, slightly OT note, you can simulate various kinds of > >> problems with these examples: > >> > >> http://linux-net.osdl.org/index.php/Netem > >> > >> Hth, > >> > >> Martin Glazer wrote: > >>> Hi, > >>> > >>> I'm experiencing some network issues and I'm trying to track them down > >>> - have run tcpdump and been checking logs, but to no avail. I suspect > >>> that there could be something now physically wrong with the network. The > >>> issues are intermittent. > >>> > >>> Does anyone know how I can go about testing the lower levels - what > >>> equipment do I need, can I rent it, is there a company in Calgary that > >>> does this? > >>> > >>> I know this is not directly related to Linux, we are running on a Linux > >>> network. > >>> > >>> Thanks > >>> > >>> Martin > >>> _______________________________________________ clug-talk mailing list [email protected] http://clug.ca/mailman/listinfo/clug-talk_clug.ca Mailing List Guidelines (http://clug.ca/ml_guidelines.php) **Please remove these lines when replying
