NWT Quiz - Chapter 7

Which two characteristics describe Ethernet technology? (Choose two.)

• <p>It typically uses an average of 16 Mbps for data transfer rates.

• It uses unique MAC addresses to ensure that data is sent to the appropriate destination.

• It is supported by IEEE 802.3 standards.

• It is supported by IEEE 802.5 standards.

• It uses a ring topology

Answer explanation

The 802.3 Ethernet standard specifies that a network implement the CSMA/CD access control method. Each node on the network has a unique MAC address for communication purposes.

What statement describes a characteristic of MAC addresses?

• They are added as part of a Layer 3 PDU.

• They are only routable within the private network.

• They have a 32-bit binary value

• They must be globally unique

What is the special value assigned to the first 24 bits of a multicast MAC address transporting an IPv4 packet?

• 01-5E-00

• 01-00-5E

• FF-00-5E

• FF-FF-FF

Answer explanation

Just as with multicast IP addresses, there is a special assigned value for multicast MAC addresses. The first 24 bits are set in hex to: 01-00-5E. The remaining 6 hex digits are derived from the lower 23 bits of the IP multicast.

What will a host on an Ethernet network do if it receives a frame with a unicast destination MAC address that does not match its own MAC address?

• <p>It will forward the frame to the next host.

• It will strip off the data-link frame to check the destination IP address.

• It will discard the frame

• It will remove the frame from the media

Answer explanation

In an Ethernet network, each NIC in the network checks every arriving frame to see if the destination MAC address in the frame matches its own MAC address. If there is no match, the device discards the frame. If there is a match, the NIC passes the frame up to the next OSI layer.

Which network device makes forwarding decisions based on the destination MAC address that is contained in the frame?

• router

• switch

• repeater

• hub

Answer explanation

Switches are the central connection point for a LAN and they maintain a MAC address table. The MAC address table has a port number associated with a MAC address for each particular device. The switch inspects a frame to look at the destination MAC address. The switch then looks in its MAC address table and if that MAC address is found, the switch forwards the data to the port that is associated with that particular MAC address.

Which network device has the primary function to send data to a specific destination based on the information found in the MAC address table?

• switch

• hub

• router

• modem

Answer explanation

If a MAC address is found in the MAC address table, then data is sent to the associated switch port. If the MAC address is not found in the MAC address table, the data is sent to all switch ports that have devices attached to the same network.

Which function or operation is performed by the LLC sublayer?

• It adds a header and trailer to a packet to form an OSI Layer 2 PDU.

• It performs data encapsulation.

• It is responsible for media access control

• It communicates with upper protocol layers.

Answer explanation

The Ethernet LLC sublayer has the responsibility to handle communication between the upper layers and the lower layers of the protocol stack. The LLC is implemented in software and communicates with the upper layers of the application to transition the packet to the lower layers for delivery.

What happens to runt frames received by a Cisco Ethernet switch? 

• The frame is broadcast to all other devices on the same network.

• The frame is returned to the originating network device.

• The frame is sent to the default gateway.

• The frame is dropped

Answer explanation

In an attempt to conserve bandwidth and not forward useless frames, Ethernet devices drop frames that are considered to be runt (less than 64 bytes) or jumbo (greater than 1500 bytes) frames. 

What addressing information is recorded by a switch to build its MAC address table?

• the destination Layer 3 address of incoming packets

• the source Layer 2 address of incoming frames

• the destination Layer 2 address of outgoing frames

• the source Layer 3 address of outgoing packets

Answer explanation

A switch builds a MAC address table by inspecting incoming Layer 2 frames and recording the source MAC address found in the frame header. The discovered and recorded MAC address is then associated with the port used to receive the frame.

What is auto-MDIX? 

• a feature that detects Ethernet cable type

• an Ethernet connector type

• a feature to automatically determine speed and duplex

• a type of Cisco switch

Answer explanation

Auto-MDIX is a feature that is enabled on the latest Cisco switches and that allows the switch to detect and use whatever type of cable is attached to a specific port.