Network Kaput -- Help!

  • Thread starter Thread starter Marek Williams
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Marek Williams

I have a small home-based book publishing business. I print the books
on a couple of large Laserjets over my little home network (to the
JetDirect cards). Everything was working fine up to two days ago, the
last time I printed something. Today I went to print an invoice and
all I could get is an error message. I tried to ping the printer and
got no response. I turned on the other printer and got the same
results.

There is only one computer, which has a 10/100 ethernet card. This
card is connected to a Zonet 8-port switch. The two printers are also
connected to this switch, and the cable modem as well. (I.e., I'm
using only four ports.)

With the printers turned on, the lights on the switch light up, as
well as on the JetDirect cards. The light on the network card is also
lit up. And the light on the switch for the cable modem is also lit.

The cable modem is still working fine. I can go anywhere on the
internet. But I can't communicate with either of the printers. As I
said, two days ago I printed without a problem. Something has happened
in the past two days. There have been no hardware changes, nor have I
installed or removed any software.

I've tried restarting the computer (Windows 2000 Professonal, SP3),
but it didn't make any difference. I also unplugged and reconnected
the cables, but that didn't help either. Anyway, it is unlikely that
it is cables, as that would mean that two different cables (to the two
printers) both chose the same exact moment to crap out. Ditto for the
JetDirect cards -- for two to go out at the same time is just about
impossible.

I also moved the cables on the switch to different ports, and it
didn't make any difference. Since the cable modem is on the switch and
it still works fine, the switch doesn't sound like the culprit. And of
course, since the cable modem is working through the NIC and the
switch, then the NIC must be all right, too.

Since it seems unlikely that it's a hardware problem, the logical
conclusion is that there must be something screwy with the networking
setup. Again, however, I have made no changes, so I'm at a loss to
figure out what could have gone wrong.

There is one other factor. On 9/22 I signed up for and installed
internet cable service (Comcast). After the installer left I noticed
that he had unplugged my switch from the NIC and plugged the modem in
there instead. He had made a comment during the setup that he didn't
understand my network, but I didn't take note at the time what he was
doing. After I discovered what he had done I took the modem out of the
NIC and plugged it into the switch, then plugged the switch back into
the NIC. However, I have printed successfully since then, so something
else must have happened.

The day after the cable was installed, I downloaded and installed the
McAfee firewall that is free for Comcast users. However, when I
discovered today that the network was broken, I disabled the firewall
completely, and it made no difference. Besides, I have printed
successfully since installing the firewall. I mention it only because
it is all I can think of.

I really need to do some printing and am getting pretty desperate.
I've spent half a day trying to figure out what is wrong without
success. I'm at my wit's end (OK, it's a short trip to the end of my
wits), and I need some suggestions. Can someone please give me some
ideas? Some new things to poke at? Even if your suggestion is not the
right one, it might help me stumble on the correct solution. Help!
 
Do you have Windows 2000 automatically search for, download, and install
the critical OS updates available from MS? Did you apply any service
patches manually that you've neglected to mention?

Find your $NTUninstall$ folders and see if any are dated within the past
few days. If so, attempt to uninstall those.

Are the JetDirects called by name (//JetDirect_Name/Printer1) or by IP
address (//192.168.0.100/Printer)? Or by some other method? Can you ping
the JetDirect's IP address?

And for crimminy-sakes, make an image backup of your system before you
apply SP4 for Win2K! You'll thank me for this advice!
 
Do you have Windows 2000 automatically search for, download, and install
the critical OS updates available from MS? Did you apply any service
patches manually that you've neglected to mention?

Find your $NTUninstall$ folders and see if any are dated within the past
few days. If so, attempt to uninstall those.
Click to expand...

No, I turned that stuff off long ago.
Are the JetDirects called by name (//JetDirect_Name/Printer1) or by IP
address (//192.168.0.100/Printer)? Or by some other method? Can you ping
the JetDirect's IP address?
Click to expand...

Couldn't even ping.
And for crimminy-sakes, make an image backup of your system before you
apply SP4 for Win2K! You'll thank me for this advice!
Click to expand...

Advice noted. I'm in no rush. Everything is working and I see no need
to install something that I hear has problems.

As to the original problem, it is resolved, as I posted in response to
another poster. It turns out that I needed a router. (OK, I'm dumb
about networking.)

However, I do have another question. Now that I have the router
working and configured, am I safe on the internet? In the process of
troubleshooting the original problem I uninstalled the McAfee firewall
that came free for Comcast users. I've had bad experiences with
firewalls in the past (ZoneAlarm), and I'd rather not reinstall the
McAfee firewall. The router does not have a built in firewall. I'm
unclear whether the router alone isolates me and gives me protection,
or if I should add a firewall on my computer as well.
 
Here's how it works:
Somebody punches in a range of IP addresses that will probe for open ports.
Or a virus wants to exploit a known vulnerability in some badly written
core component of something that Microsoft wrote (IIS, SQL Server,
whatever). Yes, your Cable/DSL router will receive this data packet. But
since it does not know what machine in your LAN it should go to, it
effectively discards it. (Your router can assign a machine to receive
packets sent to your IP based on port numbers.)

However, once a machine on your LAN has opened a port to the outside world,
packets coming back as a response may or may not have exactly what you
asked for, and in some cases, additional data packets using the same port
number may even slip through.

There are additional functions a firewall may perform: e-mail attachment
renaming, Usetnet newsgroup decoding renaming, but especially, if there is
no application to receive the incoming packet that managed to slip through
the router, the firewall will block it.

Lastly, a firewall not only stops unknown incoming packets, it also stops
unauthorized applications from sending out packets. Unauthorized
applications may include viruses, trojans, and spying programs. Some of the
latest worms, however, have figured out how to kill your firewall without
you knowing about it.

So, yes, you are protected to a fantastic degree by how your router
naturally works. It serves as a very good door. But when you open the door
and accept responses to your requests for web pages, e-mail, ftp files,
whatever, that's when the firewall come into play.

Brian Smither
Smither Consulting
 
So, yes, you are protected to a fantastic degree by how your router
naturally works. It serves as a very good door. But when you open the door
and accept responses to your requests for web pages, e-mail, ftp files,
whatever, that's when the firewall come into play.
Click to expand...

Thanks for the response. I'm going to reinstall the McAfee firewall
then.
 
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