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Computer Networks > Lesson 4 — module 1-7 > Flashcards

Lesson 4 — module 1-7 Flashcards

1
Q

What address does the data link frame use when devices are on the same Ethernet network?

A

The actual MAC address of the destination NIC.

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2
Q

Where are MAC addresses stored?

A

MAC addresses are physically embedded into the Ethernet NIC and are used for local addressing.

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3
Q

What is the source MAC address in a data link frame on the same Ethernet network?

A

It is the MAC address of the device originating the frame on the link.

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4
Q

What is the destination MAC address in a data link frame when devices are on the same link?

A

It is the MAC address of a device on the same link as the source, even if the final destination is remote.

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5
Q

What does it mean when the source and destination have a different network portion?

A

This means they are on different networks.

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6
Q

What does Layer 3 provide to Layer 2 when the destination is on a different IP network?

A

The IP address of the local default gateway (router).

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7
Q

What is the role of the default gateway in a LAN?

A

It serves as the “door” or “gateway” to all remote networks beyond the local LAN.

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8
Q

Why must all devices on a LAN know the default gateway address?

A

So their traffic can reach destinations outside the LAN.

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9
Q

What happens after Layer 2 on a device like PC1 forwards the frame to the default gateway?

A

The router begins the routing process to deliver the data to the remote destination.

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10
Q

Is data link (Layer 2) addressing local or global?

A

It is local to each link or hop and changes at every segment.

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11
Q

In the first segment of communication, what are the source and destination MAC addresses?

A

No, Layer 3 addressing remains the same end-to-end.

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12
Q

Why does data link (Layer 2) addressing change at each hop?

A

Because it is local addressing, so each segment between devices (hops) has its own source and destination MAC addresses.

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13
Q

What are the source and destination MAC addresses for the first segment of the journey?

A
  • Source: PC1 NIC (sending the frame)
  • Destination: First router’s default gateway interface (receiving the frame)
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14
Q

What are the source and destination MAC addresses for the second segment (hop)?

A
  • Source: First router’s exit interface (sending the frame)
  • Destination: Second router (receiving the frame)
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15
Q

What are the source and destination MAC addresses for the final segment of the journey?

A
  • Source: Second router’s exit interface (sending the frame)
  • Destination: Web Server NIC (receiving the frame)
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16
Q

Does the Layer 3 (IP) address change from hop to hop?

A

No, the Layer 3 IP address stays the same throughout the journey.

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17
Q

What part of the data is modified at each hop during transmission?

A

The Layer 2 frame (including MAC addresses) is modified, not the Layer 3 packet.

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18
Q

What is the main function of the Physical Layer in the OSI model?

A

To transport bits across the network media.

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19
Q

What does the Physical Layer do with a complete frame from the Data Link Layer?

A

It encodes the frame as a series of signals to be transmitted over the local media.

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20
Q

At what point in the encapsulation process does the Physical Layer operate?

A

It is the final step in the encapsulation process.

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21
Q

What does the next device in the path do after receiving bits from the Physical Layer?

A

It re-encapsulates the frame and determines how to forward it.

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22
Q

What are the 3 types of copper cabling?

A

Un shielded Twisted-Pair (UTP) cable, Shielded Twisted-Pair (STP) cable, and Coaxial Cable

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23
Q

What is the most common type of networking media?

A

UTP Cable

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24
Q

What type of connector is used to terminate a UTP cable?

A

RJ-45 connector.

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25
What does UTP typically connect in a network?
Hosts with intermediary network devices.
26
What is the purpose of the outer jacket in a UTP cable?
To protect the copper wires from physical damage.
27
Why are the wires in a UTP cable twisted into pairs?
To help protect the signal from interference.
28
What is the role of color-coded plastic insulation in UTP cables?
It electrically isolates the wires from each other and identifies each pair.
29
How does STP compare to UTP in terms of noise protection?
STP provides better noise protection than UTP.
30
What are two disadvantages of STP compared to UTP?
STP is more expensive and harder to install than UTP.
31
What type of connector is used to terminate STP cables?
RJ-45 connector.
32
What does STP typically connect in a network?
Hosts with intermediary network devices.
33
What is the purpose of the outer jacket in STP cabling?
To protect the copper wires from physical damage.
34
What is the purpose of the braided or foil shield in STP?
To provide EMI (Electromagnetic Interference) and RFI (Radio Frequency Interference) protection.
35
What is the role of the foil shield on each wire pair in STP?
It offers additional EMI/RFI protection for each twisted pair.
36
Why does STP use color-coded plastic insulation?
To electrically isolate the wires and identify each pair.
37
What does the Coaxial cable consists of?
An outer cable, a woven copper braid, a layer of plastic insulation, and a copper conductor
38
What is the purpose of the outer cable jacket in a coaxial cable?
To prevent minor physical damage to the cable.
39
What is the role of the woven copper braid or metallic foil in a coaxial cable?
It acts as the second wire in the circuit and serves as a shield for the inner conductor.
40
What is the purpose of the flexible plastic insulation in a coaxial cable?
To insulate the inner copper conductor and protect it from physical damage and interference.
41
What does the copper conductor in a coaxial cable do?
It transmits the electronic signals through the cable.
42
What are some common types of connectors used with coaxial cable?
Various connectors can be used, depending on the application, but the most common are BNC, F-type, and RCA.
43
What is one common use of coaxial cable in wireless installations?
It is used to attach antennas to wireless devices.
44
How is coaxial cable commonly used in cable internet installations?
It is used for customer premises wiring in cable internet installations.
45
How many wire pairs are in a UTP cable?
Four pairs of color-coded copper wires.
46
What is the purpose of twisting the wire pairs in UTP?
To limit crosstalk and electromagnetic interference (EMI/RFI).
47
What is "cancellation" in UTP cables?
Each wire in a pair carries opposite polarity (positive and negative), and the magnetic fields cancel each other out to reduce interference.
48
How does variation in twists per foot help in UTP cabling?
It reduces crosstalk by ensuring each pair has a different twist rate, preventing consistent interference patterns.
49
What are the two types of fiber media?
Single-Mode Fiber (SMF) and Multimode Fiber (MMF)
50
What type of fiber has a very small core?
Single-Mode Fiber (SMF).
51
What type of applications is Single-Mode Fiber best suited for?
Long-distance applications.
52
Which type of fiber has a larger core?
Multimode Fiber (MMF).
53
What kind of light source does Multimode Fiber use?
Less expensive LEDs.
54
How do LEDs transmit light in Multimode Fiber?
At different angles.
55
What is the maximum data rate and distance supported by MMF?
Up to 10 Gbps over 550 meters.
56
What is dispersion in fiber optics?
The spreading out of a light pulse over time.
57
How does dispersion affect signal strength?
Increased dispersion causes increased signal loss.
58
Which has more dispersion: SMF or MMF?
Multimode Fiber (MMF).
59
What type of communication does the Data Link Layer manage?
Communication between end-device network interface cards (NICs).
60
What does the Data Link Layer provide to upper layer protocols?
Access to the physical layer media.
61
What does the Data Link Layer encapsulate?
Layer 3 packets (IPv4 and IPv6) into Layer 2 frames.
62
What role does the Data Link Layer play in error management?
It performs error detection and rejects corrupted frames.
63
What is a data link frame field?
A specific type of frame, or a packet, used in the data link layer (Layer 2) of the OSI model
64
What is the purpose of the Frame Start and Stop field?
To identify the beginning and end of a frame.
65
What does the Addressing field indicate in a frame?
The source and destination nodes.
66
What is the role of the Type field in a frame?
To identify the encapsulated Layer 3 protocol (e.g., IPv4 or IPv6).
67
What does the Control field in a frame do?
It identifies flow control services.
68
What does the Data field of a frame contain?
The frame payload (actual data being transmitted).
69
What is the purpose of the Error Detection field?
To detect transmission errors.
70
What is another name for a Layer 2 address?
Physical address.
71
Where is the Layer 2 address found in a frame?
In the frame header.
72
What is the Layer 2 address used for?
Local delivery of a frame on the link.
73
What happens to the Layer 2 address as the frame is forwarded through the network?
It is updated by each device that forwards the frame.
74
What is the minimum size of a valid Ethernet frame (excluding the preamble)?
64 bytes.
75
What is the maximum size of a valid Ethernet frame (excluding the preamble)?
1518 bytes.
76
What happens to collision fragments or runt frames?
They are automatically discarded.
77
What are frames with more than 1500 bytes of data called?
Jumbo frames or baby giant frames.
78
What happens if a frame is smaller than the minimum or larger than the maximum allowed size?
The receiving device drops the frame.
79
What usually causes invalid Ethernet frames?
Collisions or other unwanted signals.
80
Are jumbo frames supported by modern Ethernet hardware?
Yes, most Fast Ethernet and Gigabit Ethernet switches and NICs support them.
81
How many bits are in an Ethernet MAC address?
48 bits, typically shown as 12 hexadecimal characters.
82
What is the hexadecimal range for a single byte (8 bits)?
From 00 to FF in hexadecimal (00000000 to 11111111 in binary).
83
How is the binary value 0000 1010 written in hexadecimal?
0A in hexadecimal.
84
What are the different ways hexadecimal numbers can be represented?
With 0x prefix (e.g., 0x73), a subscript 16 (e.g., 7316), or an H suffix (e.g., 73H).
85
What is the purpose of MAC addressing in an Ethernet LAN?
To identify devices at the data link layer of the OSI model.
86
How long is an Ethernet MAC address in bits and bytes?
48 bits or 6 bytes, expressed as 12 hexadecimal digits.
87
What ensures MAC addresses are unique across devices?
Each vendor registers with the IEEE to obtain a unique Organizationally Unique Identifier (OUI).
88
What are the two parts of a MAC address?
- First 6 hex digits (24 bits): Vendor's OUI - Last 6 hex digits (24 bits): Vendor-assigned unique value
89
What two MAC addresses are included in an Ethernet frame header?
The Source MAC address and the Destination MAC address.
90
How does a NIC determine if it should accept a received Ethernet frame?
It checks if the destination MAC address matches its own stored MAC address.
91
What happens if the destination MAC address doesn't match the NIC’s MAC address?
The frame is discarded.
92
Which special destination MAC addresses will a NIC also accept besides its own?
Broadcast addresses and multicast group addresses the host is part of.
93
Which devices have Ethernet NICs and MAC addresses?
Workstations, servers, printers, mobile devices, and routers.
94
What is a unicast MAC address in Ethernet?
A unique address used when a frame is sent from one device to one specific destination.
95
What protocol is used to find a destination MAC address for an IPv4 address?
ARP (Address Resolution Protocol).
96
What protocol is used to find a destination MAC address for an IPv6 address?
ND (Neighbor Discovery).
97
What type of MAC address must always be used as the source in a frame?
A unicast MAC address.
98
What is the destination MAC address for an Ethernet broadcast frame?
FF-FF-FF-FF-FF-FF (48 ones in binary).
99
Who receives an Ethernet broadcast frame on a LAN?
Every device on the Ethernet LAN processes it.
100
How does a switch handle Ethernet broadcast frames?
It floods the frame out of all ports except the incoming port.
101
Are Ethernet broadcast frames forwarded by routers?
No, routers do not forward Ethernet broadcast frames.
102
What does an IPv4 broadcast packet contain in its destination address?
An address with all ones in the host portion, targeting all hosts on the local network.
103
What is the destination MAC address prefix for an IPv4 multicast frame?
01-00-5E
104
What is the destination MAC address prefix for an IPv6 multicast frame?
33-33
105
Can multicast MAC addresses be used as the source address in Ethernet frames?
No, the source address is always a unicast.
106
How does a switch normally handle multicast Ethernet frames?
It floods the frame to all ports except the incoming port, unless configured for multicast snooping.
107
Will a router forward multicast Ethernet frames?
Not by default – it must be configured to route multicast packets.
108
What do multicast MAC addresses represent?
A group of devices (host group) that are part of a multicast group.
109
What layer does a Layer 2 Ethernet switch operate on to make forwarding decisions?
Layer 2 (Data Link Layer) using MAC addresses.
110
What is the MAC address table also known as?
Content Addressable Memory (CAM) table
111
How does a switch learn MAC addresses?
By examining the source MAC address of incoming frames and noting the port number.
112
What happens when the source MAC address already exists but on a different port?
The switch updates the entry with the new port number.
113
How long does a MAC address remain in the table by default?
5 minutes
114
What does a switch do if the destination MAC address is in the table?
Forwards the frame out the associated port.
115
What is an unknown unicast?
A frame with a destination MAC not in the MAC table, causing the switch to flood it out all ports except the incoming one.
116
How does a switch handle broadcast and multicast frames?
Floods them out all ports except the one it was received on.
117
What does filtering mean in switching?
The process of only forwarding a frame out the specific port when the destination MAC address is known.

Computer Networks (6 decks)

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