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Re: Network frustration



On 05-Oct-97 Craig Sanders wrote:
>
>my guess is that your problem may be broken DNS, mostly because of the
>telnet delay. is named still running on your name server machine? can it
>resolve hostnames and ip addresses? can other machines on the network
>use it to resolve names? are all the zone files intact? any errors in
>/var/log/daemon.log? check /etc/resolv.conf on the server, too...is it
>pointing at the correct name server?

You can rule out a traffic flood by simply pulling the connection to the
outside world. Then see if your internal services perk up.

>
>another possibility is that you have another faulty ethernet card
>somewhere on your network - it's odd to get 2 or more cards die at the
>same time...maybe you had a lightning strike nearby or some bizarre
>voltage spike on your ethernet, maybe induced voltage from running
>your cables too close to a huge coil/transformer/electrical motor or
>something like that (these are only guesses, of course)

Have you added another machine to the network that is plugged into a different
mains power circuit? If you are using coax for your ethernet, the shield is
running at power-line ground.  If there is a difference in ground potential
between two systems on the ethernet, you have a recipie for disaster. Same goes
for any serial cables that you might have added to a terminal that is plugged
into a different power circuit, many manufacturers of serial devices do not
properly isolate pin-1 from pin-7 (on a DB-25 connector) and can cause ground
loops.

Example, if you run a coax to your buddy next door, you might have serious
trouble if there is a diffefence betwen the ground circuits in the two houses.
Even something as minor as a bad connection in a power strip can cause trouble.

If you have a voltmeter, you might remove the coax connection at each machine,
one at a time, and measure between the connector shell and the computer
chassis. If you read more than a volt or so, you might have trouble. Replace
the connector before checking the next machine.


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