ARASH HABIBI LASHKARI
PUBLICATIONS
  Qualifications and Certificates
  Technical Committee Member
  Professional Experience
  Research & Developme
  Awards and Honors
  In the News
  Pulications
  Teaching
  Supervising
  Workshops
  Auxiliary Activities
Introduction to Computer Networks - RJ-45 Cableling
There are generally three main types of networking cables: straight, crossover, and rollover cables. Each cable type has a distinct use, and should not be used in place of another.

1. Straight-Through or patch cable :
Straight-through cables get their name from how they are made. Out of the 8 pins that exist on both ends of an Ethernet cable, each pin connects to the same pin on the opposite side. Review the diagram below for a visual example:
Bus
Straight-Through or patch cable
Straight-through cables are primarily used for connecting unlike devices. A straight-through cable is typically used in the following situations:
Connecting a router to a hub
Connecting a computer to a switch
Connecting a LAN port to a switch, hub, or computer
Note that some devices such as routers will have advanced circuitry, which enables them to use both crossover and straight-through cables. In general, however, straight-through cables will not connect a computer and router because they are not “unlike devices.”

2. Crossover Cable:
Crossover cables are very similar to straight-through cables, except that they have pairs of wires that crisscross. This allows for two devices to communicate at the same time. Unlike straight-through cables, we use crossover cables to connect like devices. A visual example can be seen below:
Bus
Crossover cable
As you can see, a cross over cable is configured with 4 of the wires in the same order on each end. The other four wires are crossed (hence the name). Notice how all we did was switch the orange-white and green-white wires, and then the orange and green wires. This will enable like devices to communicate. Crossover cables are typically used in the following situations:
Connecting a computer to a router
Connecting a computer to a computer
Connecting a router to a router
Connecting a switch to a switch
Connecting a hub to a hub
While the rule of thumb is to use crossover cables with like devices, some devices do not follow standards. Others provide support for both types of cables. However, there is still something that both crossover and straight-through cables can’t do.

3. Rollover Cable:
In the Cisco world, a rolled cable is a cable used to manage a router or switch from the console port of that device. This cable is usually used when configuring one of these devices for the first time. A rolled cable connects the PC’s serial port (using a DB9 to RJ45 adaptor) to the router or switch’s console port. A rolled cable looks just like an Ethernet cable. The funny thing is that a rolled cable isn’t an Ethernet cable at all. In fact, it is a serial cable. In a rolled cable, Pin 1 connects to Pin 8 on the other side. Rollover cables, also called Yost cables that allows a programmer to make a connection to the router or switch, and program it as needed, A visual example can be seen below:
Bus
Rollover Cable
Notice that each wire is simply “rolled over.” These types of cables are generally not used very much, so are usually colored differently from other types of cables. Cisco has another RJ-45 cable type namely “RJ-45 to DB-9 Female” that also known as “management cable”.
--------------------------------------------------------------
Highlights
RJ-45 Cabeling
Straight-Through
patch cable
Crossover Cable
Rollover Cable
Yost cable
New Brunswick, Canada     A.Habibi.L@gmail.com    A_Habibi_L@hotmail.com