CCNA cap. 4-7 tutto insieme

What is the process called when data moves down the layers from the Application layer to the Physical layer?

Encapsulation.

In the process of encapsulation, what is the PDU (Protocol Data Unit) called at the Transport Layer?

Segments.

In the process of encapsulation, what is the PDU called at the Network Layer?

Packet.

In the process of encapsulation, what is the PDU called at the Data Link Layer?

Frame.

In the process of encapsulation, what is the PDU called at the Physical Layer?

Bits.

Which components make up an Ethernet Frame?

Destination MAC, Source MAC, Destination IP, Source IP, User data (Packet), and FCS (Frame Check Sequence).

What is Bandwidth?

The capacity of a medium to carry data in a given amount of time. It is typically measured in kilobits per second (kb/s) or megabits per second (Mb/s).

What is the fundamental unit of bandwidth?

Bits per second (b/s).

Define Throughput.

The measure of the transfer of bits across the media over a given period of time (including amount and type of traffic).

Define Latency.

The amount of time, including delays, for data to travel from one given point to another.

Define Goodput.

The measure of usable data transferred over a given period of time; it is calculated as throughput minus traffic overhead for establishing sessions, acknowledgements, and encapsulation.

What is the signaling method?

The method used by the physical layer to generate the electrical, optical, or wireless signals that represent the "1" and "0" bits on the media.

How are data signals transmitted in a synchronous communication method?

Data signals are sent along with a clock signal which occurs at evenly spaced time durations, referred to as the bit time.

How are data signals transmitted in an asynchronous communication method?

Data signals are transmitted without an associated clock signal. Frames require start and stop indicator flags because the spacing between data characters or blocks may be of arbitrary duration.

What type of physical signals are used by copper cable?

Electrical Signals.

What type of physical signals are used by fiber-optic cable?

Light Pulse.

What type of physical signals are used by wireless media?

Microwave Signals (using Amplitude Modulation (AM), Frequency Modulation (FM), or Phase Modulation (PM)).

Which organization officially adopted RJ connectors (e.g., RJ-11, RJ-45) and the ISO 11801 network cabling standard?

ISO.

Which organization governs the TCP/IP standards implemented in software?

IETF.

Which organization co-developed the 568-C RJ-45 pinouts standard with EIA/TIA?

ANSI.

Which standard organization is responsible for 802.3 (Ethernet), 802.11 (WLAN/Wi-Fi), and 802.15 (Bluetooth)?

IEEE.

Which organization is responsible for telecommunications cabling standards (like TIA/EIA 568-C, TIA-569-B, and TIA-942)?

EIA/TIA.

What are two common external interferences that negatively affect copper cabling?

Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) (due to sources like fluorescent lights or electric motors).

What is Crosstalk?

Interference caused by the proximity of two wires, where an electromagnetic wave in one wire interferes with the signal in the adjacent wire.

How do Unshielded Twisted-Pair (UTP) cables limit the negative effect of crosstalk without using shielding?

By employing Cancellation and Varying the number of twists per wire pair.

What are the two types of UTP cable termination standards defined by EIA/TIA for RJ-45 connectors?

T568A and T568B.

What is a Straight-through (Patch) cable and when is it used?

It has the same wiring standard (A or B) applied at both ends. It is used to connect dissimilar devices (e.g., a PC and a Switch/Hub), where the TX pins of one device align with the RX pins of the other.

What is an Ethernet Crossover cable and when is it used?

It uses T568A on one end and T568B on the other, crossing pairs 2 and 3. It is used to connect similar devices (e.g., two Switches, two Hubs, two Routers, or two PCs) which have TX/RX pins in the same positions.

What is the application of a Rollover cable?

It is a Cisco proprietary cable used to connect a workstation serial port to a router or switch console port using an adapter.

What are the maximum supported speeds and distance for UTP cabling?

Supports bandwidths from 10 Mb/s up to 10 Gb/s over relatively short distances (1–100 meters).

Which type of copper media is terminated with BNC, N type, and F type connectors?

Coaxial cable.

Which cable type provides bandwidth performance up to 100 MHz and is suitable for 10BASE-T, 100BASE-TX, and 1000BASE-T (Gigabit Ethernet)?

CAT 5e.

Which copper cable category is characterized by double shielding and supports transmissions up to 1200 MHz, making it ideal for 40GHz Ethernet connections?

Category 7-7a.

What is the core structure of a fiber-optic cable?

It consists of the Core, surrounded by the Cladding, then the Buffer, strengthening material, and finally the Jacket.

What are the key characteristics of Single-mode fiber (SMF)?

Small core (9 microns), less dispersion, suited for long distance applications (up to 100,000 meters), and uses lasers as the light source.

What are the key characteristics of Multimode fiber (MMF)?

Larger core (50/62.5 microns), allows multiple paths for light, suited for long distance applications but shorter than single-mode (up to 2,000 meters), and uses LEDs as the light source.

Name three common types of fiber optic connectors.

ST Connectors (older bayonet style), SC Connectors (Subscriber/Square Connector, push-pull mechanism), and LC Connector (Lucent/Local Connector, small size).

List three common issues that can affect fiber optic media implementation.

Misalignment (fibers not precisely aligned), End gap (media not completely touching), and End finish (media ends not well polished or dirt present).

How does fiber-optic cabling compare to UTP cabling in terms of immunity to electrical hazards and EMI/RFI?

Fiber optic cabling has High immunity (it is completely immune) while UTP has Low immunity.

What is the media access control process used by IEEE 802.11 (Wi-Fi)?

Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA).

Which IEEE standard defines the Bluetooth technology?

802.15.

What maximum speed and frequency are supported by the IEEE 802.11g standard?

54 Mb/s at 2.4 GHz.

What maximum speed and frequency are supported by the IEEE 802.11ac standard?

1 Gb/s at 5 GHz.

What is the primary role of the Data Link Layer (Layer 2)?

To prepare network data for the physical network and control how data is placed and received on the media. It accepts Layer 3 packets and packages them into frames.

The Data Link Layer is divided into two sublayers. Name them.

The Logical Link Control (LLC) sublayer (upper) and the Media Access Control (MAC) sublayer (lower).

What is the function of the LLC Sublayer?

It communicates with the network layer (Layer 3) and places information in the frame that identifies which network layer protocol (like IPv4 or IPv6) is being used.

What is the function of the MAC Sublayer?

It defines the media access processes performed by the hardware, provides data link layer addressing, and handles access to various network technologies (like Ethernet or Wi-Fi).

What is the difference between a Physical Topology and a Logical Topology?

Physical topology indicates how devices are physically connected (e.g., point-to-point or star). Logical topology refers to the way frames are transferred within the network.

What is the difference between Half-duplex and Full-duplex communication?

Half-duplex restricts data exchange to one direction at a time. Full-duplex allows sending and receiving of data to happen simultaneously.

Which networking devices typically operate in Full-duplex mode?

Ethernet switches.

Which networking devices typically operate in Half-duplex mode?

Devices in legacy bus topologies, Ethernet hubs, and devices in WLANs.

Which media access control method requires nodes to operate in half-duplex, allowing only one device to send data at a time?

Contention-based access.

Within a Data Link Frame, what is the purpose of the Type field?

It identifies the Layer 3 protocol (e.g., IPv4 or IPv6) contained in the data field.

Within a Data Link Frame, what is the purpose of the Control field?

It specifies special flow control services, such as Quality of Service (QoS).

Which two OSI layers does Ethernet operate in?

The Data Link Layer and the Physical Layer.

What are the two sublayers Ethernet is based upon?

The Logical Link Control (LLC) and the Medium Access Control (MAC) sublayers.

Which IEEE standard defines the Logical Link Control (LLC) sublayer?

IEEE 802.2.

Which IEEE standard defines the MAC sublayer and physical specifications?

IEEE 802.3.

What are the three main functions provided by the Data Encapsulation process at the MAC sublayer?

Frame delimitation; Addressing (using MAC addresses); and Error detection (using CRC).

What is the primary method used by Ethernet to control how nodes share access to the medium?

Carrier Sense Multiple Access (CSMA).

What type of network access is Ethernet considered, meaning any device can try to transmit data whenever it has data to send?

A contention-based (non-deterministic) method.

What does CSMA/CD stand for, and when is it used?

Carrier Sense Multiple Access/Collision Detection. It is used in Ethernet networks; but is considered superfluous in modern LANs.

What does CSMA/CA stand for, and when is it primarily used?

Carrier Sense Multiple Access/Collision Avoidance. It is used in wireless networks (802.11).

What is the MAC Address also known as, since it is burned into the ROM of the Network Interface Card (NIC)?

Burned-in Address (BIA).

How is a MAC address structured?

It is a 6-byte (48-bit) hexadecimal address; divided into a 3-byte Organizationally Unique Identifier (OUI) assigned by the manufacturer; and 3 bytes assigned uniquely to the interface.

What is the size range (in bytes) of a standard Ethernet frame?

Minimum 64 bytes and maximum 1518 bytes.

What is a "collision fragment" or "runt frame"?

Any frame less than 64 bytes in length; which is automatically discarded by receiving stations.

What is the function of the Frame Check Sequence (FCS) field in an Ethernet frame?

It uses the Cyclic Redundancy Check (CRC) to detect errors in the frame.

What does the Type field in an Ethernet II frame header identify?

The higher-layer protocol being encapsulated (e.g.; 0x0800 for IPv4; 0x86DD for IPv6; 0x0806 for ARP).

Which MAC address is used for a Broadcast communication in Ethernet?

FF-FF-FF-FF-FF-FF (all Fs).

Which MAC address range indicates a Multicast frame?

A special value that begins with 01-00-5E in hexadecimal.

What is the logical topology of an Ethernet network, which implies shared media access?

A bus with multiple access.

What is the physical topology of most modern Ethernet networks?

A star or extended star topology; where end devices connect to a Layer 2 LAN switch.

On what basis does a Layer 2 LAN switch perform filtering and forwarding decisions?

Only on the Layer 2 (Data Link) MAC address.

What is the term sometimes used for the MAC Address Table, particularly in Cisco devices?

Content Addressable Memory (CAM).

How does a Layer 2 switch dynamically build its MAC address table?

By examining the source MAC address of incoming frames and recording it along with the incoming port number.

If a switch receives a frame and the source MAC address already exists in the table but on a different port, how does the switch handle it?

The old entry is replaced with the same MAC address and the newest port number.

What happens if a switch receives a frame destined for a Unicast MAC address NOT found in its table?

The switch forwards (floods) the frame out of all ports except the incoming port. This is known as an unknown unicast.

What happens if a switch receives a frame destined for a Broadcast or Multicast MAC address?

The frame is flooded out of all ports except the incoming port.

What must the switch do if the destination MAC address IS found in the MAC address table?

It forwards the frame only through the specific port associated with that destination MAC address.

What are the two primary traditional methods used by switches to forward data between network ports?

Store-and-forward switching and Cut-through switching.

Describe Store-and-forward switching.

The switch receives and stores the entire frame in a buffer before forwarding it. It performs an error check (CRC) on the frame's integrity.

What is the main advantage of Store-and-forward switching?

It conserves bandwidth by discarding corrupted frames; preventing them from consuming bandwidth across the network.

What is the main advantage of Cut-through switching?

It is the faster switching method.

Describe Cut-through switching.

The switch begins forwarding the data as soon as the destination MAC address (first 6 bytes after the preamble) is read.

What is the main disadvantage of Cut-through switching?

It does not perform error checking (CRC) and may forward corrupted frames onto the network; consuming bandwidth.

Which forwarding method is the only one used on current Cisco Catalyst switch models?

Store-and-forward switching.

What is Shared Memory Buffer?

A buffering method where all frames are deposited in a common memory buffer shared by all switch ports; allowing for dynamic linking to the destination port and generally reducing frame loss.

What is Asymmetric switching?

A feature allowed by Shared Memory Buffer that permits different data transmission speeds on different ports (e.g.; dedicating higher bandwidth to a server port).

In Full Duplex communication, how does data flow?

Data flow is bidirectional (sent and received simultaneously).

What state is the collision detection circuit in when operating in Full Duplex mode?

It is disabled (collision-free) because the two communicating nodes use separate circuits.

What are the three duplex settings supported by a Cisco Catalyst switch?

full (Full-duplex mode); half (Half-duplex mode); and AUTO (automatically decides the best operating mode).

What is the purpose of the auto-MDIX command?

When enabled; the switch detects the type of copper Ethernet cable needed (straight-through or crossover) and automatically configures the interface accordingly.

What is Power over Ethernet (PoE)?

A feature that allows a switch to provide power to a device (like IP phones or wireless access points) over the Ethernet cable; increasing installation flexibility.

What is the Forwarding Rate of a switch?

The processing capacity of a switch; defining the amount of data it can handle per second.

What is a Fixed Configuration Switch?

A switch whose features and ports cannot be added to or changed beyond what was originally provided.

What is a Modular Configuration Switch?

A switch that offers flexibility by using a chassis that accepts different-sized line cards; which contain the ports.

What is an SFP (Small Form-Factor Pluggable) module?

A transceiver module supported by switches (like the Catalyst 3560) that allows connection flexibility; supporting various fiber-optic and copper standards (e.g.; 100BASE-FX; 1000BASE-T).

How does a Layer 3 Switch differ from a Layer 2 switch?

A Layer 3 switch uses both the Layer 2 MAC address and Layer 3 IP address information to make forwarding and routing decisions.

What functions can Layer 3 switches perform on a LAN, potentially reducing the need for dedicated routers?

They can perform Layer 3 routing functions as quickly as they perform switching.