network resources

Kevin Colby kevinc at
Tue Dec 19 17:18:02 GMT 2000

Charles Crawford wrote:
> I can ping the clients by ip, or if I include the ip/host names in the
> /etc/hosts file, but not through DNS... our DNS is external.

Are you sure this is not the problem?  Red Hat systems will execute
a reverse lookup on all tcp connection attempts, and the connection
will be held up pending this lookup or a time-out.  If you really want
to be sure this isn't the problem, verify that a telnet attempt from
the same Windows client does not exhibit a long lag before prompting
for a login.  You will always be able to ping by IP, whether your
reverse lookups work or not.

> I've thought about this, but that's not the issue... what is actually
> happening, I believe, is that the ping from the Win client is going to
> the WINS server, then to the linux box, back to the WINS server, and
> then on back to the client.

Try a traceroute?  I find it hard to believe this is happening.

> The response time being doubled indicates to me that the traffic is
> traveling twice the distance, not being held up somewhere... BTW, it
> is EXACTLY twice the time, so I think that that indicates an extra
> trip for each packet to the destination machine.

This could easily be something else, though.  What about half vs.
full-duplex network cards/drivers and/or 10/100 and hub/switch
differences?  Assuming it is a network issue, is the route to and
from each of these machines through the same type of equipment?

> Oh, I had another non-related question regarding RH, and that is that
> I recently read something about an ftp server issue that allows the
> server to become overloaded or something. I have noticed a rather
> large number of FTP error messages in the log files at times and was
> wondering where I could get more information about this.

If you're running RH, watch the errata:
(There was a 6.2 FTP exploit fix released in June.)

	- Kevin Colby
	  kevinc at

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