What type of cables to use between hubs, switches, routers and workstations / pc / computer?

The type of cable table

Back to the fundamentals. Here’s a quick reference of what type of cable to use in what situation. Most modern networking equipment nowadays have auto MDI/MDIX which automatically detects and switches to cross-over or straight through. However, if one side of the device has the duplex and speed settings hard coded, it could render the auto MDI/MDIX feature useless.

So here’s a table with all the combinations and the type of cable to use:

 Hub  Switch Router  Workstation / PC
 Hub  Crossover  Crossover  Straight  Straight
 Switch  Crossover  Crossover  Straight  Straight
 Router  Straight  Straight  Crossover  Crossover
 Workstation / PC  Straight  Straight  Crossover  Crossover

In general when you connect two similar devices ie, switch to switch, router to router, workstation to workstation, you will use a cross-over cable, and for all others – use a straight through. That’s a good way to remember what to use.

Layer 1 Basics

In order to understand more complex network technologies it is important to have a strong understanding of the basics.

So here we are Layer 1 – Ethernet, the most commonly used access medium for LAN network. An Ethernet cable consists of a Cat5/Cat5e/Cat6 cable and a RJ45 connector. The cable comprises of 4 twisted copper pairs totaling 8 pins.

The 10Base-T and the 100Base-TX standard both use 2 pairs, one pair to transmit and one pair to receive.

Note that in a straight through setting, the transmit pair occupies pins 1 and 2. The receive pair occupies 3 and 6. Pairs 4,5 and 7,8 are left unused. In order to connect two PCs together, a crossover cable should be used by basically connecting the transmit pair from one side to the receive pair on the other side and vice versa.

The mappings in a crossover cable are Pins 1-3, 2-6, 3-1, and 6-2.

Modern Cisco switches and router interfaces support Auto-MDIX (Auto medium-dependent interface crossover) which automatically detects and swaps the receive and transmit pairs when a wrong cable is used.

RJ-45 Copper Ethernet cables

Copper cables are usually much cheaper compared to fiber and are often used for shorter distance patch cabling. Cat 1 – 4 are being omitted as they are not commonly deployed nowadays as they do not support 100 Mb Base-T.

Category 10/100 Mb Fast Ethernet 100BASE-TX 1 Gb (1000 Mb) Gigabit Ethernet 1000BASE-T 10 Gb Ethernet 10GBASE-T
Cat5 100 meters Not Supported Not Supported
Cat5E 100 meters 100 meters Not Supported
Cat6 100 meters 100 meters 55 meters
Cat6A 100 meters 100 meters 100 meters
Cat7 (Shielded) 100 meters 100 meters 100 meters
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