Q5: Intro to Ethernet and Switching

Question 1

Which two of the following are equivalent to a megabyte (choose two)

A. 1000 Kilobytes
B. 8000 Kilobits
C. 1000 bits
D. 8000 bits

Answer 1

Answer:
A) 1000 kilobytes
B) 8000 kilobits

Explanation: 1 Megabyte = (1000) x 1 Kilobyte = 1000 kilobytes. 1000 kilobytes x 8 bits/byte = 8000 kilobits

Question 2

Which of the following are valid mac address? (choose two)

A. 02F9.3351.AG86
B. A2:17:BB:69:02:C5
C. 00C0.1B5A.84E8
D. 28-F1-25-A0-4H-33

Answer 2

Answer:
B) A2:17:BB:69:02:C5
C) 00C0.1B5A.84E8

Explanation: There are a few different formats that you may see mac addresses written in, such as:

xxxx.xxxx.xxxx
xx:xx:xx:xx:xx:xx
xx-xx-xx-xx-xx-xx

But remember that mac addresses are made up of hexadecimal characters, so no letters above “F”

Question 3

Describe how a switch builds its mac-address table.

Answer 3

Explanation:

When a switch receives a frame, it verifies that the source address in the frame is recorded in its mac-address table. If it is not in the table, then the switch will record the mac address, the vlan and the port number from where the frame originated and store the info in the mac-address-table for a default of 5 minutes. The switch then uses the information in this table to make forwarding decisions.

Question 4

Which bits in the mac addresss 00c0.12d5.e398 identify the company that manufactured the NIC?

A.e398
B. d5e398
C. 00c12
D. 00c0

Answer 4

Answer:

c) 00c012

Explanation: There are 12 characters in a mac address and the first 6 are the OUI (organizational Unit Identifier) which identify the original equipment manufacturer of the NIC.

Question 5

How would you reconfigure the mac address on the Ethernet NIC of a windows host?

A. You must use the Microsoft tool MacEdit

B. It can be reconfigured from a command prompt

C. MAC Addresses are “burned in” and cannot be reconfigured

D. The system administrator is the only one allowed to reconfigure the MAC address

Answer 5

Answer:
C) MAC addresses are “burned in” and cannot be reconfigured.

Explanation: IP addresses are logical constructs that can be configured and changed at will. MAC addresses, however, are addresses that are “burned in” to the NIC and are not reconfigurable. Although the mac cannot be reconfigured, it is possible for a hacker to spoof a mac address- that is use a hacker’s application to put a source mac address in a frame that is different than the real mac address of the NIC