[lug] Linux boxes drop off the net? Router problem?

[Sebastian Sobolewski]

> > Our SysAdmin is pretty good in many respects, but I think he'd be the first
> > to say that he falls short of the "guru level" in some areas -- Linux is
> > definitely one of them, and I don't think he knows everything there is to
>
>Who would ...
>
>BTW, is it possible that some of your boxes are misconfigured? I have
>seen similar phaenomena in a network where two boxes happened to have
>the same hardware address (yes, thatr _is_ possible). Some intelligent
>route inbetween got really confused. Similar things happen if two boxes
>share the same IP address. Or does the IP address of your gateway change
>sometimes? Or even worse: do two gateways share the same IP address?
>The kernel keeps a cache of the hardware addresses it has seen recently,
>if the kernel thinks the hardware addresss of box A is xx:xx:xx:xx:xx:xx
>when in reality it changed then it keeps sending the IP addresses to the
>wrong hardware address.

         But that should have an effect on both sides of the connection 
should it not?  Ie: not being able to ping out from the machine in question 
as well as ping in.  He seems to only have the problem of the machine 
disappearing from the network externally. (Not being able to ping the 
machine from another one, but he can ping from that "invisible" machine to 
anything else) Also after the ping the machine becomes visible again to the 
external net.  This would indicate that the configuration problem is at the 
3com switch.  Right?

         I'm curious to see what the cause and solution to this problem is 
as well.

-Sebastian
Sebastian Sobolewski