CompTIA Network+ Network+ Ethernet Switching Features 3 — Questions and Answers
Question 1: Which protocol provides automatic negotiation of EtherChannel parameters between two directly connected switches?
- LACP (802.3ad) (Correct answer)
- STP
- VTP
- CDP
Correct answer: LACP (802.3ad)
LACP (Link Aggregation Control Protocol, IEEE 802.3ad) dynamically negotiates EtherChannel link bundles between switches.
Question 2: What happens to traffic on a VLAN when that VLAN is not in the allowed VLAN list on a trunk link?
- Traffic is forwarded with a default tag
- Traffic is dropped and not forwarded across the trunk (Correct answer)
- Traffic is placed in the native VLAN automatically
- Traffic triggers a VLAN mismatch alarm
Correct answer: Traffic is dropped and not forwarded across the trunk
If a VLAN is not included in the trunk's allowed VLAN list, frames tagged with that VLAN ID are dropped at the trunk interface.
Question 3: A network administrator notices a switch port cycling between up and down states rapidly. Which STP feature would detect this condition and disable the port?
- PortFast
- BPDU guard (Correct answer)
- Loop guard
- Root guard
Correct answer: BPDU guard
BPDU guard disables a PortFast-enabled port if it receives a BPDU, placing it in err-disabled state to prevent topology issues.
Question 4: In a campus network, which switch role is responsible for aggregating access-layer switches and connecting them to the core?
- Access switch
- Distribution switch (Correct answer)
- Core switch
- Edge switch
Correct answer: Distribution switch
The distribution layer switch aggregates traffic from multiple access switches and applies policies before forwarding to the core.
Question 5: What does the native VLAN on an 802.1Q trunk carry?
- Management traffic only
- Untagged frames (Correct answer)
- Frames tagged with VLAN 1 exclusively
- All inter-VLAN routed traffic
Correct answer: Untagged frames
Untagged frames received on an 802.1Q trunk are assigned to the native VLAN; frames sent for the native VLAN are transmitted untagged.
Question 6: Which switch feature forwards traffic based on a combination of source/destination MAC, IP, and port to distribute load across multiple uplinks?
- Spanning Tree load balancing
- EtherChannel with a hashing algorithm (Correct answer)
- VLAN trunking with round-robin
- OSPF ECMP routing
Correct answer: EtherChannel with a hashing algorithm
EtherChannel uses a configurable hashing algorithm (e.g., src-dst-mac, src-dst-ip) to distribute frames across bundled physical links.
Question 7: A switch port is configured with the command 'switchport mode dynamic desirable'. What will this port do when connected to another switch port set to 'dynamic auto'?
- Remain an access port on both ends
- Form a trunk because desirable actively initiates trunking (Correct answer)
- Form a trunk only if manually forced on the other end
- Shut down due to a mode mismatch
Correct answer: Form a trunk because desirable actively initiates trunking
Dynamic desirable actively negotiates trunking via DTP; when connected to dynamic auto (which passively waits), the desirable side initiates and a trunk is formed.
CompTIA Network+ Network+ Ethernet Switching Features 3
Which protocol provides automatic negotiation of EtherChannel parameters between two directly connected switches?