ccna-notes

Interfaces and Cables

Table of contents

• Network Protocols
• Bits and Bytes
• Ethernet
• Cable Standards
• Copper UTP Cables
• Fiber-optic UTP Cables
• UTP vs Fiber-optic Cabling

Network Protocols

Agreed upon system of communicating between network devices.

Bits and Bytes

• Bit = 0 or 1
• Byte = 8 bits

Speed

Ethernet

Collection of network protocols/standards that fit in RJ-45 ports.

• RJ = “Registered Jack”

Cable Standards

• defined in the IEEE 802.3 standard in 1983
• IEEE = Institute of Electrical and Electronics Engineers

Copper UTP Cables

Type of copper cables used in ethernet standards.

• Unshielded = no metallic shield, which makes them vulnerable to electrical interference
• Twisted Pair = Literaly 4 pairs of wires with each pair twisted together, protecting against EMI (Electromagnetic Interference)
• 8 pins, perfect for the number of wires

• Not all ethernet cables use all 8 wires

  

Copper cable standards

• “BASE” refers to baseband signaling (outside of CCNA scope) and “T” refers to “twisted pair”

10BASE-T and 100BASE-T

• Full-Duplex transmission: both connected devices can receive and transmit data at the same time

Straight-through cable connections

1 --- 1
2 --- 2

3 --- 3
6 --- 6

Crossover cable connections

1 --- 3
2 --- 6

3 --- 1
6 --- 2

Auto MDI-X 🔥

Truth is that most modern network devices don’t need to worry about straight-through or crossover cables because of Auto MDI-X.

It allows deviced to automatically detect which pins their neighbor is transmiting data on, and then adjust which pins to use to transmit/receive data.

1000BASE-T and 10GBASE-T

In addition to using ALL pairs of wires, each pair is BI-DIRECTIONAL. This is part of the reason why they can operate at much faster speeds.

1 --- 1
2 --- 2

3 --- 3
6 --- 6

4 --- 4
5 --- 5

7 --- 7
8 --- 8

Fiber-optic UTP Cables

Connections

• 1 : Fiber glass core, where light is transmitted
• 2 : Cladding that reflects light
• 3 : Protective buffer
• 4 : Outer jacket of the cable

Single-mode

• Narrower core than multimode
• Single angle (mode) from laser-based transmitter
• Allows longer cables than UTP and multimode
• More expensive than multimode fiber (laser-based sfp transmitters)

Multimode

• Wider fiber glass core than single-mode fiber
• Allows multiple angles (modes) of light waves to enter the fiber glass core
• Allows longer cables than UTP
• Shorter cables than single-mode fiber
• Cheaper than single-mode fiber (led-based sfp transmitters)

Fiber-optic Cable standards

UTP vs Fiber-optic Cabling

UTP	Fiber-optic
Cheaper	More expensive
Shorter max distance (~100m)	Longer max distance
Vulnerable to EMI	EMI proof
RJ45 ports are cheaper than SFP ports	SFP ports are more expensive (and single-mode ir more expensive than multimode)
Leak faint signal outside of cable (security risk)	No signal leak