switch connectivity problem (help)

My setup:

I have a P1 computer that I use as a firewall and dhcp server
(smoothwall.org), connected to des-1008d d-link (8 port switch).
And anther computer (laptop) connected to the switch.

Scenario 1:
If I use 3meter patch cables, I get connectivity between my firewall
and laptop. (via switch)

As follows
firewall--(straight cat 5 3m cable)--switch--(straight cat 5 3m
cable)--Laptop

Scenario 2:
If I was the same setup but with a longer cable, (I.e. firewall and
switch in one room, and computer in anther room dist ~ 20m), I do not
get connectivity.

As follows:
firewall--(straight cat 5 3m cable)--switch--(straight cat 5 3m
cable)--(rj-45 socket)--(long straight cat 5 cable)--(rj-45
socket)--(straight cat 5 3m cable)--LAPTOP

ps: no led on switch from laptop side.

Scenario 3:
As an experiment, I used scenario 2, but without the switch, and using
cross over cable (since pc to pc).

As follows:

firewall--(cross-over cat 5 cable)--(rj-45 socket)--(long straight cat
5 cable)--(rj-45 socket)--(straight cat 5 3m cable)--LAPTOP

I get Connectivity.

At the beginning I thought the problem in the cat 5 (long wire), but
from scenario 3, I could eliminate it.

An the switch is working when everything at small range.

I get the problem when I want to connect at a longer range.
but ~20 meter is hardly considered a long range!!

ps: I tried to use anther switch (d-link dss-8+) I get the same
problem.

I am new to networks, am I missing anything, any suggestion is
appreciated

Thanks

victor wrote:

 > My setup:
 >
 > I have a P1 computer that I use as a firewall and dhcp server
 > (smoothwall.org), connected to des-1008d d-link (8 port switch).
 > And anther computer (laptop) connected to the switch.
 >
 > Scenario 1:
 > If I use 3meter patch cables, I get connectivity between my firewall
 > and laptop. (via switch)
 >
 > As follows
 > firewall--(straight cat 5 3m cable)--switch--(straight cat 5 3m
 > cable)--Laptop
 >
 > Scenario 2:
 > If I was the same setup but with a longer cable, (I.e. firewall and
 > switch in one room, and computer in anther room dist ~ 20m), I do not
 > get connectivity.
 >
 > As follows:
 > firewall--(straight cat 5 3m cable)--switch--(straight cat 5 3m
 > cable)--(rj-45 socket)--(long straight cat 5 cable)--(rj-45
 > socket)--(straight cat 5 3m cable)--LAPTOP
 >
 > ps: no led on switch from laptop side.
 >
 > Scenario 3:
 > As an experiment, I used scenario 2, but without the switch, and using
 > cross over cable (since pc to pc).
 >
 > As follows:
 >
 > firewall--(cross-over cat 5 cable)--(rj-45 socket)--(long straight cat
 > 5 cable)--(rj-45 socket)--(straight cat 5 3m cable)--LAPTOP
 >
 > I get Connectivity.
 >
 > At the beginning I thought the problem in the cat 5 (long wire), but
 > from scenario 3, I could eliminate it.
 >
 > An the switch is working when everything at small range.
 >
 > I get the problem when I want to connect at a longer range.
 > but ~20 meter is hardly considered a long range!!
 >
 > ps: I tried to use anther switch (d-link dss-8+) I get the same
 > problem.
 >
 > I am new to networks, am I missing anything, any suggestion is
 > appreciated
 >
 > Thanks

The logical approach you are taking seems to be a good one.

Some devices are more tolerant of poor signals than other devices,
so your crossover experiment may have worked because the laptop
and/or firewall have better noise tolerance than the switches.

The fact that the led(s) on the laptop side of the switch indicate
no connection in scenario 2 really cries out to me that the problem is
with the long cable.

If you wired your own long cable, I would check to confirm that you
maintained the pairings (i.e. that you connected the wires precisely
according to the color code specified in 568-A or -B). Also make sure
you didn't untwist more than was necessary.

Assuming your network runs at 100Mbps, an experiment you might try is to
force the laptop in scenario 2 to run at 10Mbps (assuming you have that
capability -- if not, you could perhaps insert a 10Mbps hub on that end
to force it) and see if you suddenly can connect -- that would confirm
that the cable is the problem.

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