Mod7

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

• the destination Layer 3 address of incoming packets
• the destination Layer 2 address of outgoing frames
• the source Layer 3 address of outgoing packets
• the source Layer 2 address of incoming frames

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 are the two sizes (minimum and maximum) of an Ethernet frame? (Choose two.)

• 56 bytes
• 64 bytes
• 128 bytes
• 1024 bytes
• 1518 bytes

Answer explanation

The minimum Ethernet frame is 64 bytes. The maximum Ethernet frame is 1518 bytes. A network technician must know the minimum and maximum frame size in order to recognize runt and jumbo frames.

What are two methods for switching data between ports on a switch? (Choose two.)

• cut-off switching
• cut-through switching
• store-and-forward switching
• store-and-supply switching
• store-and-restore switching

Answer explanation

The two methods for switching data between ports on a switch are cut-through switching and store-and-forward switching.

What feature automatically negotiates the best speed and duplex setting between interconnecting devices?

• auto-MDIX
• autobots
• autonegotiation
• autotune

Answer explanation

Autonegotiation is a technology that automatically negotiates the speed and duplex between two connected devices.

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

• The frame is dropped.
• The frame is returned to the originating network device.
• The frame is broadcast to all other devices on the same network.
• The frame is sent to the default gateway.

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 is a function of the MAC sublayer? (Choose three.)

• controls access to the media
• checks for errors in received bits
• uses CSMA/CD or CSMA/CA to support Ethernet technology
• communicates between software at the upper layers and the device hardware at the lower layers
• allows multiple Layer 3 protocols to use the same network interface and media

Answer explanation

The MAC sublayer checks for bit errors, supports Ethernet technologies, and controls access to the media.

What is auto-MDIX?

• a type of Cisco switch
• an Ethernet connector type
• a type of port on a Cisco switch
• a feature that detects Ethernet cable type

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

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

• 01-5E-00
• FF-00-5E
• FF-FF-FF
• 01-00-5E

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 statement describes a characteristic of MAC addresses?

• They must be globally unique.
• They are only routable within the private network.
• They are added as part of a Layer 3 PDU.
• They have a 32-bit binary value.

Answer explanation

Any vendor selling Ethernet devices must register with the IEEE to ensure the vendor is assigned a unique 24-bit code, which becomes the first 24 bits of the MAC address. The last 24 bits of the MAC address are generated per hardware device. This helps to ensure globally unique addresses for each Ethernet device.

What type of address is 01-00-5E-0A-00-02?

• an address that reaches every host inside a local subnet
• an address that reaches one specific host
• an address that reaches every host in the network
• an address that reaches a specific group of hosts

Answer explanation

The multicast MAC address is a special value that begins with 01-00-5E in hexadecimal. It allows a source device to send a packet to a group of devices.