ICND1 LAN Switching Technologies 4 — Questions and Answers
Question 1: A trunk link between two switches carries VLANs 1–100. Which command restricts it to carry only VLANs 10, 20, and 30?
- switchport trunk native vlan 10,20,30
- switchport trunk allowed vlan 10,20,30 (Correct answer)
- switchport trunk vlan permit 10,20,30
- vlan trunk allow 10,20,30
Correct answer: switchport trunk allowed vlan 10,20,30
The 'switchport trunk allowed vlan' command specifies which VLANs are permitted to traverse the trunk.
Question 2: Which STP port role carries the best path toward the root bridge on a non-root switch?
- Designated port
- Alternate port
- Root port (Correct answer)
- Backup port
Correct answer: Root port
Each non-root switch has one root port, which is the port with the lowest-cost path to the root bridge.
Question 3: What does the 'switchport mode dynamic desirable' command cause the port to do?
- Force the port to be an access port
- Actively attempt to form a trunk using DTP (Correct answer)
- Passively wait for a trunk negotiation
- Disable DTP on the port
Correct answer: Actively attempt to form a trunk using DTP
'Dynamic desirable' causes the port to actively send DTP frames to negotiate a trunk with the neighbor.
Question 4: Which feature prevents a non-root switch port from immediately transitioning to forwarding when it first connects, avoiding temporary loops?
- BPDU Guard
- Root Guard
- Spanning Tree Protocol (Correct answer)
- Loop Guard
Correct answer: Spanning Tree Protocol
STP's listening and learning states introduce a delay before forwarding to ensure a loop-free topology is established.
Question 5: Two switches are connected with an EtherChannel bundle. Which load-balancing method uses both source and destination MAC addresses?
- src-mac
- dst-mac
- src-dst-mac (Correct answer)
- src-dst-ip
Correct answer: src-dst-mac
The 'src-dst-mac' load-balancing method hashes both source and destination MAC addresses to select the active link.
Question 6: What is the default VTP mode on a Cisco Catalyst switch?
- Client
- Transparent
- Off
- Server (Correct answer)
Correct answer: Server
Cisco switches default to VTP Server mode, allowing them to create, modify, and delete VLANs.
Question 7: Which attack technique allows a host to send frames on a VLAN it should not access by exploiting trunk negotiation?
- MAC flooding
- ARP poisoning
- VLAN hopping via double tagging (Correct answer)
- STP root takeover
Correct answer: VLAN hopping via double tagging
Double-tagging attacks embed an inner VLAN tag that gets processed after the outer tag is stripped at the first trunk.
ICND1 LAN Switching Technologies 4
A trunk link between two switches carries VLANs 1–100.
Which command restricts it to carry only VLANs 10, 20, and 30?