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Old 07-26-2004, 07:29 PM   #1
Registered: Jun 2004
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when to use cross over or straight through cable.

for PC to PC I know it's cross over.
Switch to switch,router to router cross-over??
all other straight through?

thus pc to switch straight through.
and switch to wall outlet striaght through also?
Old 07-26-2004, 07:45 PM   #2
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Best thing to do is check the manuals. Newer hardware can autodetect the type of cable. Some hardware has a special port called an UPLINK port. This port is used to conect hubs and switches together. These UPLINK ports need to be crossover cables unless otherwise noted. Some hardware has mechanical switches to change between crossover and a straight cable on the uplink port. The same thing goes for routers.

PCs to hubs, switches, routers and wall outlets are usually straight through cables.
Old 07-27-2004, 04:57 AM   #3
Registered: Jan 2004
Location: North Yorkshire, UK
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As michaelk says, newer hubs, routers, etc. can determine the cable type. However he's made a small mistake. Uplink ports are wired as NICs and need a straight cable to connect to another hub (assuming the other hub is not connected via the uplink port).

Effectively, the basis is as follows:

NIC - wired as NIC
HUB (or switch) - wired as HUB
Router with single port - wired as NIC
Router with built in hub - wired as HUB
Uplink port on hub - wired as NIC

Then work as follows:
NIC to HUB - Straight cable
NIC to NIC - Xover cable
HUB to HUB - Xover cable

In effect, a HUB port has the cross over within itself, a NIC doesn't.

As you can see, the purpose of an uplink port is to allow you to connect it to another hub via a straight cable. HOWEVER if you connect uplink to uplink, you're back to a Xover cable.

Ignore wall boxes etc. They should all present the same type as the device they are wired back to, so if your wall box is wired back to a normal port on the hub (switch) then it presents as a HUB, if it's wired back to an uplink port (Why?) then it presents as a NIC.

Old 07-27-2004, 02:27 PM   #4
Registered: Sep 2002
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simple formula
normally there are 2 categories of devices

1.Pcs and routers
2.switches and hubs

if u want to connect any device within its group then crossover cable is needed.
if u want to connect two devices which are not in same group then staraight through cable.
Old 05-09-2006, 01:57 AM   #5
Registered: Oct 2004
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I used to believe that to connect two PCs we have to use crossover cable (since they are similar devices).

Today 9-05-2006 I figured out that the straight through cable is working as well I tried this between a lapto and a Desktop.

Any clarification about this ?

I assigned ip address of type and

And I tried also ip and


1- Laptop NIC is : Broadcom 570x Gigabit Integrated Controller.

2- Desktop NIC#1 is : Intel(R) PRO/100 VE Desktop Connection.

3- Desktop NIC#2 is : D-Link DFE-528TX PCI Adapter

I connected between Broadcom 570x Gigabit Integrated Controller and Intel(R) PRO/100 VE Desktop Connection.

And then i have connected between Broadcom 570x Gigabit Integrated Controller and D-Link DFE-528TX PCI Adapter

Last edited by zillah; 05-09-2006 at 02:18 AM.
Old 05-09-2006, 02:56 AM   #6
Registered: Jan 2004
Location: North Yorkshire, UK
Distribution: Centos 5
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Some more modern devices have an autodetection ability for the cable. They sense the NIC/HUB input and adjust connections accordingly. Typical of these are routers with inbuilt hubs, almost all of them are now autosensing.

It seems as though at least one of your NICs (probably the Broadcom) is autosensing and hence works with the straight through cable.



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