Sunday, June 22, 2014

What kind of cable do I need?

What kind of cable do I need?


This is just an example of the progress of time and the evolution of networking equipment. Back in the day it used to be mandatory to use a crossover cable between switches and routers and between some servers and hubs, but modern equipment can autosense the connection type and change it's mdx configuration on a per port basis. Therefore newer training materials will list a standard cable as the proper connection.

I still advise you keep a crossover cable handy though in your travels since you never know when you will meet an older piece of equipment that may require that type of connection.

Good luck with your studies,

To kind of tie into what was said, you should get in the habit of always using the suggested cable type. If you don't then you could spend hours troubleshooting an issue that could have been avoided by using the correct type. It is nice when the devices auto-configure for you, but you do not want to get in the habit of relying on it.
To flex my newly acquired networking muscle...I will shed some light on this topic (I don't have too many networking muscles).

True, auto-sensing ports eliminate the need to think about whether you're using cross over or straight through. But, as mentioned, it is probably safer to practice good networking rules.

Note: The correct method to connect a router to a switch is by using a straight through cable. Switches and Hubs transmit on pins 3 & 6, where as pretty much any other NIC's and Router's transmit on pins 1 & 2.

So :

router to router....crossover

PC to PC....crossover

switch to switch.....crossover

PC to router....crossover

PC to switch, Router to switch, PC to Hub....straight-through
This topic has to do with the OSI Model.

You are dealing with the 3 bottom most layers. Network, Data Link, and Physical.

Routing is done at Layer 3. (IP addressing)
Switching is done at Layer 2 (Mac Addresses, ARP, Etc.)
Cables fall under layer 1. (Fiber, Copper, NIC)

Cross-over cables are used for same layer transfer. (e.g. Layer 2 - Layer 2 and Layer 3 - Layer 3)

Straight through cables are used for different layer transfer(one of many uses) (e.g. Layer 2 to Layer 3)

Auto sensing ports (where available) make life a little easier by doing away with the guess work and layer thinking. I work on a network backbone, so we try not to rely on auto sensing ports to much (its just something else to fail)


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