NWC204

BÀI TẬP
1. What happens If the size of a transmitted frame is less than the minimum, or greater than
the maximum?
If a transmitted frame's size is less than the minimum or greater
than the maximum defined by the protocol, it's considered malformed.
Oversized frames may be fragmented, while undersized ones may be
rejected or padded.
2. What are the six Ethernet Frame Fields?
Preamble
Start Frame Delimiter (SFD)
Destination MAC Address
Source MAC Address
EtherType or Length
Data Payload
Frame Check Sequence (FCS)
3. What is the Destination MAC Address Field?
The Destination MAC Address field in an Ethernet frame is a 6-byte (48-bit) field that
identifies the intended recipient of the frame.
4. What is the Source MAC Address Field?
The Source MAC Address field in an Ethernet frame is a 6-byte (48-bit) field that
identifies the sender of the frame.
5. What happens if s small packet is encapsulated.
When a small packet is encapsulated for transmission over a network, it is typically
encapsulated within a larger frame. This process occurs at different layers of the network stack,
depending on the protocols being used.
6. What is the Frame Check Sequence (FCS) used for?
The Frame Check Sequence (FCS) is used for error detection in Ethernet frames. It is a 4-
byte (32-bit) field appended to the end of the Ethernet frame. The FCS is generated based on the
contents of the frame, including the Destination MAC Address, Source MAC Address, EtherType
or Length field, and the Data Payload.
7. Which part of an Ethernet Frame uses a pad to increase the frame field to at least 64
bytes?
Data field.
8. Which part of an Ethernet frame detects errors in the frame?
Frame check sequence (FCS) field
9. Which part of an Ethernet Frame describes the higher-layer protocol that is encapsulated?
Ether type.
10. Which part of an Ethernet Frame notifies the receiver to get ready for a new frame?
The preamble.
11. Which data link sublayer controls the network interface through software drivers?
The LLC sublayer.
12. Which data link sublayer works with the upper layers to add application information for
delivery of data to higher level protocols?
The LLC sublayer.
13. What is a function of the MAC sublayer? (State three.)
Controls access to the media
Checks for errors in received bits
Uses CSMA/CD or CSMA/CA to support Ethernet technology
14. AN Ethernet MAC address is a __ bit address expressed using __ hexadecimal digits.
48-bit address 12
15. What is a unicast MAC address?
A unicast MAC address is a type of MAC address used in Ethernet networks to uniquely
identify a single network interface card (NIC) or network adapter.
16. Explain the broadcast MAC address.
The broadcast MAC address is a special MAC address used to send data frames to all
devices within the same network segment, facilitating communication between devices and
network services that require broadcast messaging.
17. Explain the multicast MAC address.
Multicast MAC addresses provide a mechanism for efficient and targeted
communication with specific groups of devices on an Ethernet network, enabling applications
and services that require multicast messaging while minimizing network bandwidth usage.
18. Explain Ethernet Switch Learning.
Ethernet switch learning is a process by which an Ethernet switch dynamically builds and
maintains a table of MAC addresses and their corresponding port associations. This process
allows the switch to efficiently forward frames to their intended destinations within a network.
19. Explain Ethernet Switch Forwarding.
Ethernet switch forwarding is the process by which an Ethernet switch receives frames
on one port and forwards them out through one or more other ports based on the destination
MAC address of each frame. This process allows the switch to selectively deliver frames to their
intended recipients within a network, improving network efficiency and reducing unnecessary
traffic.
20. When is a frame flooded to all ports (except the origin)?
A frame is flooded to all ports (except the port on which it was received) in an Ethernet
switch when the switch does not have an entry in its MAC address table for the destination MAC
address of the frame.
21. When will the switch add a new MAC address to the MAC table?
An Ethernet switch adds a new MAC address to its MAC address table whenever it
receives a frame from a device that has not been previously encountered on the network. This
process occurs during the Ethernet switch learning phase.
22. When will the switch not add the MAC address to the MAC table?
Ethernet switches typically do not add MAC addresses to their MAC address tables in
situations where the source MAC address already exists in the table, the frame contains
reserved or invalid MAC addresses, or there are concerns about MAC address spoofing and
security.
23. When will a switch drop a frame?
Destination MAC Address Not Found.
CRC Error.
Resource Exhaustion.
Port Security Violation…
24. What are the two switches method for switching data between network ports?
Store-and forward
Cut-through switching
25. What is Store and Forward Switching?
Store and Forward switching is a common and widely used switching method in Ethernet
networks, offering a balance of reliability, efficiency, and error detection capabilities.
26. What is Cut Through Switching?
Cut Through switching offers lower latency compared to Store and Forward switching,
making it suitable for time-sensitive applications.
27. What are the two variants of cut-through switching?
Strict Cut Through Switching
Fragment-Free Switching
1. Em hãy đổi các số sau từ hệ thập phân sang hệ nhị phân.

a) 200 = 1x27+1x26+0x25+0x24+1x23+0x22+0x21+0x20 = 11001000
b) 165 = 10100101
c) 176 = 10100101
d) 241 = 11110001
Ví dụ:
2. Em hãy đổi các số sau từ hệ nhị phân sang hệ thập phân.

a) 11001101 = 1x27+1x26+0x25+0x24+1x23+1x22+0x21+1x20 = 205
b) 10011011 = 155
c) 10011100 = 156
Ví dụ
3. Chuyển đổi cơ số 16 sang cơ số 10

a) BFDE = 49118
b) 9ADE = 39646
c) 8AAD = 35501
d) 3ADE = 15070
Ví dụ:
Các kiến thức cần nhớ

· Phân Lớp
+ 1-126 -> A (net_id = 1 byte, host_id = 3 byte; Subnet Mask = /8)
+ 128-191 -> B (net_id = 2 byte, host_id = 2 byte; Subnet Mask = /16)
+ 192-223 -> C (net_id = 3 byte, host_id = 1 byte; Subnet Mask = /24)
· Số địa chỉ IP hợp lệ với n bit host = 2n – 2
· Số mạng con chia được khi mượn n bit host = 2n
Dạng 1: Tính các thông số cơ bản
4. 192.29.32.30/255.255.255.201
- Tính số mạng con và số host của mạng con?
192 -> phân lớp C (net_id= 3 byte, subnet mask = /24)
Subnet mask = 255.255.255.201 = /28
Số bit host_id = 32-28 = 4
Số bit làm subnet_id: 28 - 24 =4 bit
=> Số mạng con= 24 = 16
Số host = 24 -2 = 14
5. 172.16.250.196/255.255.231.31
- Tính số mạng con và số host của mạng con?
172 -> phân lớp B (net_id= 2 byte, subnet mask = /16)
Subnet mask = 255.255.231.31 = /27
Số bit host_id = 32 -27 = 5
Số bit làm subnet_id: 27 - 16 = 11 bit
=> Số mạng con= 211 = 2048
Số host = 25 -2 = 30
Ví dụ:
Dạng 2: Các bài toán chia subnet

6. 192.48.96.0/25
- Hãy phân hoạch thành 8 mạng con
Mạng con 1: 192.48.96.0 - 192.48.96.7
Mạng con 2: 192.48.96.8 - 192.48.96.15
Mạng con 3: 192.48.96.16 - 192.48.96.23
Mạng con 4: 192.48.96.24 - 192.48.96.31
Mạng con 5: 192.48.96.32 - 192.48.96.39
Mạng con 6: 192.48.96.40 - 192.48.96.47
Mạng con 7: 192.48.96.48 - 192.48.96.55
Mạng con 8: 192.48.96.56 - 192.48.96.63
7. 172.16.156.0/16
- Hãy phân hoạch thành 4 mạng con
Mạng con 1: 172.16.0.0 - 172.16.3.255
Mạng con 2: 172.16.4.0 - 172.16.7.255
Mạng con 3: 172.16.8.0 - 172.16.11.255
Mạng con 4: 172.16.12.0 - 172.16.15.255

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BÀI TẬP

1. Em hãy đổi các số sau từ hệ thập phân sang hệ nhị phân.

2. Em hãy đổi các số sau từ hệ nhị phân sang hệ thập phân.

3. Chuyển đổi cơ số 16 sang cơ số 10

Các kiến thức cần nhớ

Dạng 2: Các bài toán chia subnet

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