Cisco CCNA Basic Switching Concepts 2 — Questions and Answers
Question 1: A switch receives a frame with a destination MAC address not in its MAC address table. What does it do?
- Drops the frame
- Floods the frame out all ports except the incoming port (Correct answer)
- Sends the frame back to the source
- Buffers the frame until the address is learned
Correct answer: Floods the frame out all ports except the incoming port
When a switch receives a frame with an unknown unicast destination, it floods the frame out all ports except the one it arrived on.
Question 2: Which switching method begins forwarding a frame before the entire frame is received?
- Store-and-forward
- Cut-through (Correct answer)
- Fragment-free
- Adaptive switching
Correct answer: Cut-through
Cut-through switching begins forwarding the frame as soon as the destination MAC address is read, without waiting for the full frame.
Question 3: What is the size of a MAC address?
- 32 bits
- 48 bits (Correct answer)
- 64 bits
- 128 bits
Correct answer: 48 bits
MAC addresses are 48 bits (6 bytes) long, typically expressed as 12 hexadecimal digits.
Question 4: Which part of a MAC address identifies the manufacturer of the network interface card?
- Last 3 bytes
- First 3 bytes (OUI) (Correct answer)
- First byte only
- Last byte only
Correct answer: First 3 bytes (OUI)
The first 3 bytes of a MAC address form the Organizationally Unique Identifier (OUI), assigned by IEEE to the manufacturer.
Question 5: A network administrator wants to prevent a switch from learning MAC addresses on a specific port dynamically. Which feature should be used?
- VLAN pruning
- Port security with sticky MAC (Correct answer)
- Spanning Tree PortFast
- DHCP snooping
Correct answer: Port security with sticky MAC
Port security with sticky MAC learning locks down dynamically learned addresses and converts them to secure sticky entries.
Question 6: What happens when the MAC address table of a switch becomes full?
- The switch reboots automatically
- New frames are dropped
- The switch floods all new unknown frames like a hub (Correct answer)
- The switch deletes the oldest VLAN entries first
Correct answer: The switch floods all new unknown frames like a hub
When the CAM table is full, the switch cannot learn new MAC addresses and floods unknown frames out all ports, effectively behaving like a hub.
Question 7: Which frame type is always flooded by a switch to all ports in the VLAN?
- Unicast frames
- Multicast frames with a known group
- Broadcast frames (Correct answer)
- Frames with TTL=1
Correct answer: Broadcast frames
Broadcast frames (destination FF:FF:FF:FF:FF:FF) are always flooded to all ports within the same VLAN.
Cisco CCNA Basic Switching Concepts 2
A switch receives a frame with a destination MAC address not in its MAC address table.
What does it do?