07 Ethernet Switching

Question 1

What are some characteristics of the Logical Link Control Layer?

Answer 1

1. Interfaces with the NIC via software drivers
2. Places information in the frame that identifies which network layer protocol is being used for the frame
3. Enables IPv4 and IPv6 to utilize the same network media
4. Adds Layer 2 control information to network protocol data

Question 2

What are some characteristics of the Media Access Control sublayer?

Answer 2

1. Responsible for sending/receiving data on the physical medium
2. Provides synchronization between source and target nodes
3. Controls access to the media through signaling and physical media standards
4. Implements a trailer for error detection
5. Supports Ethernet via CSMA/CD, CSMA/CA

Question 3

Describe the structure of a MAC address, to include:

1. the two major parts
2. the number of bits
3. the number of bytes
4. the number of hexadecimal digits

Answer 3

1. Two major parts: OUI (the first 3 bytes) and device serial number (the second 3 bytes)
2. Number of bits: 48 bits
3. Number of bytes: 6 bytes
4. Number of hex digits: 12 hex digits

Question 4

Describe the two basic switch forwarding methods.

Answer 4

Store-and-forward: the switch stores one entire incoming frame, and performs error checking before sending the frame to the next device. If the frame has transmission errors, it’s immediately dropped.

Cut-through: the switch reads the frame until the destination address is fully read. Once the switch has the destination address, it immediately forwards the frame to the next device. It does not perform any error checking on incoming frames.

Question 5

What is the value of the Ethertype field for IPv4?

Answer 5

0x0800

Ethertype value for IPv4

Question 6

What is the value of the Ethertype field for IPv6?

Answer 6

0x86DD

Ethertype value for IPv6

Question 7

What is the Ethertype value for ARP?

Answer 7

0x0806

Ethertype value for ARP