100-150 Free Practice Test

During the data encapsulation process, which OSI layer adds a header that contains MAC addressing information and a trailer used for error checking?

1. A. Network
2. B. Transport
3. C. Data Link
4. D. Session

Correct Answer: C

OSI model
During the data encapsulation process, the Data Link layer of the OSI model is responsible for adding a header that contains MAC addressing information and a trailer used for error checking. The header typically includes the source and destination MAC addresses, while the trailer contains a Frame Check Sequence (FCS) which is used for error detection1.
The Data Link layer ensures that messages are delivered to the proper device on a LAN using hardware addresses and translates messages from the Network layer into bits for the Physical layer to transmit. It also controls how data is placed onto the medium and is received from the medium through the physical hardware.
References :=
✑ The OSI Model – The 7 Layers of Networking Explained in Plain English
✑ OSI Model - Network Direction
✑ Which layer adds both header and trailer to the data?
✑ What is OSI Model | 7 Layers Explained - GeeksforGeeks

A local company requires two networks in two new buildings. The addresses used in these networks must be in the private network range.
Which two address ranges should the company use? (Choose 2.) Note: You will receive partial credit for each correct selection.

1. A. 172.16.0.0 to 172.31.255.255
2. B. 192.16.0.0 to 192.16.255.255
3. C. 11.0.0.0 to 11.255.255.255
4. D. 192.168.0.0 to 192.168.255.255

Correct Answer: AD
The private IP address ranges that are set aside specifically for use within private networks and not routable on the internet are as follows:
✑ Class A: 10.0.0.0 to 10.255.255.255
✑ Class B: 172.16.0.0 to 172.31.255.255
✑ Class C: 192.168.0.0 to 192.168.255.255
These ranges are defined by the Internet Assigned Numbers Authority (IANA) and are used for local communications within a private network123.
Given the options: A. 172.16.0.0 to 172.31.255.255 falls within the Class B private range.
* B. 192.16.0.0 to 192.16.255.255 is not a recognized private IP range. C. 11.0.0.0 to 11.255.255.255 is not a recognized private IP range. D. 192.168.0.0 to 192.168.255.255 falls within the Class C private range.
Therefore, the correct selections that the company should use for their private networks are
A and D. References :=
✑ Reserved IP addresses on Wikipedia
✑ Private IP Addresses in Networking - GeeksforGeeks
✑ Understanding Private IP Ranges, Uses, Benefits, and Warnings