[BC] IP Weirdness

[Bernie Courtney]

a few thoughts:

1.) If all your machines are intermittently losing network
connectivity, then swap out your switch, there obviously is something
wrong.
Another thing worth trying would be to try forcing the NIC's down to
100Mbit for the time being to test.  Perhaps your cabling or other
environmental factor(s) are causing the devices not to stay synced at
gigabit speeds.  Until you get to a point where you are not
intermittently loosing the link between your switch and your PC's I
wouldn't worry about anything else.

2.)what are the subnets involved?  are you perhaps trying to ping the
broadcast address for one of them?

3.)what are the OS's of the machines in question and are they part of a domain?

b


On Mon, May 26, 2008 at 11:15 AM, Jason R. <jyrussell at academicplanet.com> wrote:
> Here's an IP oddity I saw for the first time  -
> (sorry for the length, but I'm trying to accurately describe the problem).
>
>  Have you ever seen a machine try to ping a different address than what you
> put in...?
>
>  I have four XP Pro machines tied together with TCP/IP - UDP across a small
> 8 port Linksys Gig ready switch/router. As far as I know, that router
> doesn't do DHCP or assign addresses at all, it might as well be strictly a
> fast fat switch.
>
>  Internet service is provided by a jumper to a Belkin DHCP router, so there
> are 5 ports tied up on the Linksys(Cisco) switch.   Only one on the internet
> router. The internet service is Cable, with our node fixed, so I don't know
> much other way to do it.
>
>  For whatever reason, the network connection to some of the machines has
> become extremely erratic, inlhouse, on our side..  The network connectivity
> popup in the bottom corner of the screen has started going on and off every
> few seconds... "A network cable is unplugged" -  then about 10 seconds later
> "Local Area Connection 1GbPs  Status Connected" -
> On, off, On, Offf...
>
>  It had started on one machine.   I went to a spare network card.  It went
> fine for about a week, now the problems back, but on more than one machine.
>
>  Using Net View and Ping I saw what you'd expect, but... Not.    You can see
> al the machines on the net, but, it pings weird.  Internet and intra-net
> connectivity is on and off and on and off...
>
>  One specific machine address keeps pinging weird.
> Put in 'ping 192.168.0.75' - and the screen responds 'pinging
> 192.168.0.61'.... notice the difference.
> You sometimes get 4 good responses, sometimes get 1, sometimes get none.
>
>  I suspected the router, cached addresses, or something, so I changed all
> out.  Powered down all the machines. Pulled out the Linksys gig router.
> Flushed all the stuff I could by using DHCP from the internet router to each
> machine, ran ran the release all/renew stuff, then reset the correct
> addreses by hand. (the workspace software uses fixed IP's...).  and put the
> Lnksys gig switch back in the net.
>
>  Things run better, at least for now.
>
> I suspect the problem is actually on the machine a x.x.0.75 - as it has a
> program on it installed by corporate... something called NoIP.  Every
> machine  stayed happy for about 5 minutes after I did my fix, but later that
> night (via VNC) I started seeing more dropouts, and found the NoIP stuff
> phoning home a lot.
>
>  I'm tempted to turn the machine with NoIP on it off, and see if the network
> problem goes away...
>
> Jason