Ethernet Cabling

Ethernet cabling is an important discussion, especially if you are planning on taking the Cisco exams.

Three types of Ethernet cables are available:

• Straight-through cable
• Crossover cable
• Rolled cable

Straight Through

The straight-through cable is used to connect

• Host to switch or hub
• Router to switch or hub

Crossover Cable

The crossover cable can be used to connect

• Switch to switch
• Hub to hub
• Host to host
• Hub to switch
• Router direct to host

Rolled Cable

Although rolled cable isn’t used to connect any Ethernet connections together, you can use a rolled Ethernet cable to connect a host to a router console serial communication (com) port.


Data Encapsulation

When a host transmits data across a network to another device, the data goes through encapsulation:

• It is wrapped with protocol information at each layer of the OSI model.
• Each layer communicates only with its peer layer on the receiving device.

PDU


Port Numbers


The Transport layer uses port numbers to define both the virtual circuit and the upper-layer process.


Cisco’s Three-Layer Model


The following are the three layers and their typical functions:

• The core layer: backbone
• The distribution layer: routing
• The access layer: switching