NE NE Switching 1 — Questions and Answers
Question 1: What is the default port cost for a 1 Gbps link in IEEE 802.1D Spanning Tree Protocol?
- 4
- 19 (Correct answer)
- 100
- 1000
Correct answer: 19
IEEE 802.1D assigns a cost of 19 to 1 Gbps links, used by STP to determine the best path to the root bridge.
Question 2: In STP, what is the role of the Root Bridge?
- It forwards traffic between VLANs
- It serves as the reference point for all STP path calculations in the network (Correct answer)
- It provides DHCP services
- It manages trunk negotiation
Correct answer: It serves as the reference point for all STP path calculations in the network
The Root Bridge is the STP reference point; all switches calculate their best path (lowest cost) toward the root bridge to build a loop-free topology.
Question 3: Which STP port state forwards frames and learns MAC addresses?
- Blocking
- Listening
- Learning
- Forwarding (Correct answer)
Correct answer: Forwarding
Only ports in the Forwarding state both learn MAC addresses and pass user data frames.
Question 4: What does the 'show mac address-table' command display on a Cisco switch?
- Configured VLANs and their associated ports
- Dynamically learned and static MAC-to-port mappings (Correct answer)
- STP topology and port roles
- Interface duplex and speed settings
Correct answer: Dynamically learned and static MAC-to-port mappings
The MAC address table maps learned MAC addresses to the switch ports they were learned on, enabling frame forwarding decisions.
Question 5: What is the purpose of VLAN trunking using 802.1Q?
- To aggregate multiple physical links into one logical link
- To carry traffic from multiple VLANs over a single physical link by tagging frames (Correct answer)
- To prevent loops in a switched network
- To assign IP addresses to VLAN interfaces
Correct answer: To carry traffic from multiple VLANs over a single physical link by tagging frames
802.1Q inserts a 4-byte tag into Ethernet frames to identify VLAN membership, allowing multiple VLANs to traverse one trunk link.
Question 6: Which switching method begins forwarding a frame before it is fully received, reducing latency?
- Store-and-forward
- Cut-through (Correct answer)
- Fragment-free
- Adaptive cut-through
Correct answer: Cut-through
Cut-through switching begins forwarding after reading only the destination MAC address, at the cost of possibly forwarding corrupt frames.
NE NE Switching 1
What is the default port cost for a 1 Gbps link in IEEE 802.1D Spanning Tree Protocol?