Now days, LAN card has intelligence,
so that both cables can work.
They have a
feature on lots of switches and hubs etc called "auto-mdix" or
"auto mdi/mdix", that is the new thing where it doesn’t matter what
kind of cable you use, it will just auto detect the proper connection type no
matter which cable you use.
The cable
can be categorized as Cat 5, Cat 5e, and Cat 6 UTP cable. Cat 5 UTP cable can
support 10/100 Mbps Ethernet network, whereas Cat 5e and Cat 6 UTP cable can
support Ethernet network running at 10/100/1000 Mbps. You might hear about Cat
3 UTP cable, it's not popular anymore since it can only support 10 Mbps
Ethernet network.
Straight and
crossover cable can be Cat3, Cat 5, Cat 5e or Cat 6 UTP cable, the only
difference is each type will have different wire arrangement in the cable for
serving different purposes.
Ethernet
network cables are straight and crossover cable. This Ethernet network cable is
made of 4 pair high performance cable that consists of twisted pair conductors
that used for data transmission. Both end of cable is called RJ45 connector.
There are
two types of network cables commonly used in PC networks - Straight-through and
cross-over.
Straight Cable
Usually use
straight cable to connect different type of devices. This type of cable will be
used most of the time and can be used to:
1) Connect a
computer to a switch/hub's normal port.
2) Connect a
computer to a cable/DSL modem's LAN port.
3) Connect a
router's WAN port to a cable/DSL modem's LAN port.
4) Connect a
router's LAN port to a switch/hub's uplink port. (Normally used for expanding
network)
5) Connect
two switches/hubs with one of the switch/hub using an uplink port and the other
one using normal port.
If you need
to check how straight cable looks like, it's easy. Both sides (side A and side
B) of cable have wire arrangement with same color.
Crossover Cable
Sometimes
you will use crossover cable, it's usually used to connect same type of
devices. A crossover cable can be used to:
1) Connect
two computers directly.
2) Connect a
router's LAN port to a switch/hub's normal port. (Normally used for expanding
network)
3) Connect
two switches/hubs by using normal port in both switches/hubs.
In you need
to check how crossover cable looks like, both side (side A and side B) of cable
have wire arrangement with following different color.
This cable
(either straight cable or cross cable) has total 8 wires (or we can say lines),
i.e. four twisted pairs (4x2=8) with different color codes. Right now just
forget about color codes. It doesn’t matter what color is given to the cable
(but there is a standard).
In straight
cable connectivity is like as follows
RJ451
Connected to RJ452
Pin1-------------------------------------
Pin1
Pin2-------------------------------------
Pin2
Pin3-------------------------------------
Pin3
Pin4-------------------------------------
Pin4
Pin5-------------------------------------
Pin5
Pin6-------------------------------------
Pin6
Pin7-------------------------------------
Pin7
Pin8-------------------------------------
Pin8
In cross
cable connectivity is like as follows
RJ451
Connected to RJ452
Pin1-------------------------------------
Pin3
Pin2-------------------------------------
Pin6
Pin3-------------------------------------
Pin1
Pin4-------------------------------------
Pin4
Pin5-------------------------------------
Pin5
Pin6-------------------------------------
Pin2
Pin7-------------------------------------
Pin7
Pin8-------------------------------------
Pin8
Purpose of
this cross cable is RX (receiving terminal) connects to TX (transmitting) of
one pc to another PC and vice versa.
As we use
two PCs (same devices), straight cable will connect TX to TX and RX to RX of
two computers, so cross cable is required. If you use HUB or switch, then
straight cable will work because it has internal arrangement like cross cable.
So note that use cross cable to connect two similar devices.
A straight
cable will not work to connect two computers together.
Crossover used
to connect to PCs directly together, also used for connecting networking
devices together like Switch to Switch etc.
Straight cables
connect two DIFFERENT types of devices. Whereas crossover cables connect two of
the SAME type
Now do this
(if possible): connect cross cable between switch and PC and see what
happens..!
| Hub | Switch | Router | Workstation | |
| Hub | Crossover | Crossover | Straight | Straight |
| Switch | Crossover | Crossover | Straight | Straight |
| Router | Straight | Straight | Crossover | Crossover |
| Workstation | Straight | Straight | Crossover | Crossover |
-----------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------------
Communication between Switches and Workstations
When a workstation connects to a LAN, it transmits data independently of the other devices connected to the LAN media. The workstation simply transmits data frames from a NIC to the network medium.
If desired, the workstation can be attached directly to another workstation by using a crossover cable. Crossover cables connect the following devices:
- Workstation to workstation
- Switch to switch
- Switch to hub
- Hub to hub
- Router to router
- Router to PC
- Switch to router
- Switch to workstation or server
- Hub to workstation or server
Switches, which are Layer 2 devices, use intelligence to learn the MAC addresses of the devices that are attached to its ports. This data is entered into a switching table. After the table is complete, the switch can read the destination MAC address of an incoming data frame on a port and immediately forward it. Until a device transmits, the switch does not know its MAC address.
Switches provide significant scalability on a network. Switches are normally connected to each other by way of trunk links.
