The Gigabit Ethernet standard requires that all pins be connected.
So this is an example of a crossover cable four gigabit using the DT 568b standard.
Notice all pins are configured in a crossover fashion.
All four pairs of wires are used in this example.
Now, in the past, you'd have to know when to use a straight through or crossover cable.
Any of these implementations would use a straight through cable.
So router to switch.
PC to switch.
PC to bridge or PC to hub.
Any of these implementations would use a crossover cable.
So rather to rudder switch to switch PC to PC or hub to hub or bridge to switch PC to server, hub to
switch and once again, router to router all require crossover cables.
However, today, automatic crossover or auto mdex is widely used.
Auto Mdex was introduced in 1998 and it made the requirement for crossover cables obsolete.
MDI devices are typically routers or PCs.
MDI devices are typically switches or hubs, so they are medium dependent interface crossover devices.
And in the past you would need to connect an MDI device such as a PC to a switch or hub.
In the old days, once again, certain ports would have a button to flip the role from MDI to MDI,
which would allow you to connect a switch to a switch using a straight through cable.
However, today, in a lot of cases, auto MDI.
MDI allows for automatic switching once the cable is connected.
The devices can order detect the cable type, so there's no need to worry as much about cable types
today.
A straight through cable as an example, could be used between hubs or between switches.
So in the past you used to have to use a crossover cable between two switches, but that's not necessarily
required today.
Straight through cables could be used and devices would work out which side is MDI and which side is
MDX.
However, be careful.
That's not always true when on site you may encounter an older Cisco switch that doesn't support or
to MDI MDI.
So you may have to use the correct cabling type between older devices.
There are various categories of cable.
In general, the higher the category, the more twists and the less susceptible the cable is to electromagnetic
interference.
The higher the category, the more stringent the specifications are for crosstalk and system noise.
Higher cable categories typically support higher frequencies and higher speeds.
I wouldn't try to remember all the categories of cable if I were you.
Just see this as an explanation of the various categories you may encounter in networks or in documentation.
Category one was previously used for telephones and modems.
So Category one is a grade of unshielded twisted pair cabling designed for telephone communications
and was at one time the most common on premise wiring.
This is not suitable for data transmission.
Category two was previously used for telephones and data networks up to four megabits per second.
Category three was used previously for data networks up to ten megabits per second.
It's now generally used for telephones.
Category four is defined up to 20 megahertz, with speeds up to 16 megabits per second.
Category five is defined up to 100 megahertz speeds of ten or 100 megabits per second when using two
pairs and one gigabits per second when using four pairs.
Category one, two and four are no longer used.
Category three is no longer used in data networks, and generally category five is no longer used.
But there's a lot of installations that have category five, so you may still come across.
It kept five was an improvement on Cat five.
It supports frequencies up to 100 megahertz and supports speeds up to one gigabits per second.
It has a maximum distance of 100 meters and is similar to Cat five but improved the CAT five specification
by reducing noise and signal interference.
So some crosstalk was improved with the new specification.
The Category five specification improves upon the Category five specification by tightening some crosstalk
specifications and introducing new crosstalk specifications that were not present in the original Category
five specification.
The bandwidth of Cat five and Cat five is the same.
In other words, 100 megahertz, and the physical cable construction is the same.
And the reality is that most Cat five cables meet Cat five E specifications, though it may not be tested
or certified as such.
Category six defines frequencies up to 250 megahertz and increases the number of pair twists per inch
to reduce signal noise and interference.
It supports ten gigabits per second, but only up to 55 meters.
The top of specifications and Cat six guarantee 100 meter runs at one gigabits per second.
So Category six cable, commonly referred to as Cat six, is a standardised cable for gigabit Ethernet
and is backward compatible with Category five or Category five and Category three cable standards compared
to Cat five or Cat five.
Cat six features more stringent specifications for crosstalk and system noise.
The Cable Standard provides performance up to 250 megahertz and is suitable for ten bass TW 200 bass,
TCS or Fast Ethernet and 1000 bass RT or gigabit Ethernet as well as ten gigabit Ethernet Category six
A or augmented category six defined frequencies up to 500 megahertz, which is twice that of Cat six.
It also includes improvements with regards to crosstalk and support speeds up to ten gigabits per second.
But in this case, with the extended cable length of 100 meters Category six, maximum cable length
was 55 meters in a favorable environment, but only 37 meters in an environment where a lot of crosstalk
took place, such as when cables are bundled together.
So Category six A or Cat six improved the specification, allowing for ten gigabits per second up to
100 meters.
Category seven or Cat seven defined frequencies up to 600 megahertz and support speeds of up to ten
gigabits per second up to 100 meters.
The connectors in Cat seven can be terror connectors rather than eight PHC or eight position eight contact,
which we commonly referred to as an RJ 45 connector.
So here's an example of a terror connector and Cat seven notice.
The pairs of cable in Cat seven are protected by a foil shield.
The twisting of pairs and the number of turns per inch is also increased to protect from crosstalk and
in addition has a ten copper twin.
X Category seven is also known as KLOS f.
And also has a clause F a which defined frequencies up to 100 megahertz per second and which in theory
supports speeds up to 40 gigabits per second and 100 gigabits per second at 15 meters.
This is currently an ISO or ISO standard but is not recognized by the EIA.
EIA.
For brand new installations, it's generally recommended that Cat six A or Cat seven be used.
If reusing existing Cat six cabling cable segments must be tested up to 350 megahertz and limited by
TIA EIA recommendations.
Now Category eight is the next generation twisted cabling specification and is being developed to support
40 gigabits per second.
In other words, four times the speed of ten gigabit Ethernet.
The technical recommendation for Category eight was released in March 2013 and has both clause one and
clause two.
In other words, Category 8.1 cable and Category 8.2 cables.
Category 8.1 is fully backward compatible and interoperable with Category six A using RJ 45 connectors.
Category 8 to 2 is interoperable with Category seven cabling using either RJ 45 or terra connectors.