CompTIA Network+ Network+ Ethernet Switching Features 2 — Questions and Answers
Question 1: A network administrator wants to prevent a rogue DHCP server from responding to client requests on an access port. Which switch feature should be enabled?
- Port security
- DHCP snooping (Correct answer)
- Dynamic ARP inspection
- 802.1X authentication
Correct answer: DHCP snooping
DHCP snooping filters DHCP messages on untrusted ports, blocking rogue DHCP servers from responding to clients.
Question 2: Which spanning tree port state actively forwards frames and learns MAC addresses?
- Blocking
- Listening
- Learning
- Forwarding (Correct answer)
Correct answer: Forwarding
The Forwarding state is the only STP state where a port both learns MAC addresses and forwards data frames.
Question 3: A switch port is connected to an IP phone with a PC daisy-chained behind it. The phone traffic needs to be on VLAN 20 and PC traffic on VLAN 10. What port configuration is required?
- Trunk port with allowed VLANs 10 and 20
- Access port on VLAN 20 with a voice VLAN configured (Correct answer)
- Two separate access ports bridged together
- A routed port with subinterfaces
Correct answer: Access port on VLAN 20 with a voice VLAN configured
Configuring a voice VLAN on an access port allows the switch to tag voice traffic to a separate VLAN while data traffic remains untagged on the access VLAN.
Question 4: What is the purpose of the Spanning Tree Protocol PortFast feature?
- Forces a port to become the root port immediately
- Allows a port to skip the listening and learning states and go directly to forwarding (Correct answer)
- Increases the speed of STP convergence across the entire network
- Enables a port to participate in rapid STP elections
Correct answer: Allows a port to skip the listening and learning states and go directly to forwarding
PortFast skips the STP listening and learning states so end-device ports reach the forwarding state immediately upon link-up.
Question 5: Which 802.1Q field is used to carry VLAN membership information inside an Ethernet frame?
- EtherType field
- VLAN ID (VID) field within the 802.1Q tag (Correct answer)
- Source MAC address field
- Frame Check Sequence field
Correct answer: VLAN ID (VID) field within the 802.1Q tag
The 12-bit VLAN ID field within the 4-byte 802.1Q tag identifies which VLAN the frame belongs to, supporting up to 4094 VLANs.
Question 6: A switch shows excessive MAC address table churn, and unknown unicast flooding is degrading performance. What feature can limit the number of MAC addresses learned on an access port?
- Storm control
- Port security (Correct answer)
- BPDU guard
- Dynamic ARP inspection
Correct answer: Port security
Port security limits the number of MAC addresses allowed on a port and can take actions (shutdown, restrict, protect) when the limit is exceeded.
Question 7: In MSTP (Multiple Spanning Tree Protocol), what is an MST instance (MSTI)?
- A single STP domain covering all VLANs
- A logical STP topology that maps one or more VLANs to a single spanning tree (Correct answer)
- A backup root bridge for a specific VLAN range
- A timer used to synchronize STP regions
Correct answer: A logical STP topology that maps one or more VLANs to a single spanning tree
An MSTI is a distinct spanning tree instance within an MST region, allowing multiple VLANs to share a single STP calculation.
CompTIA Network+ Network+ Ethernet Switching Features 2
A network administrator wants to prevent a rogue DHCP server from responding to client requests on an access port.
Which switch feature should be enabled?