NE NE Switching 2 — Questions and Answers
Question 1: What is an inter-VLAN routing method that uses a single trunk link between a router and a switch?
- Layer 3 switching
- Router-on-a-stick (Correct answer)
- Proxy ARP routing
- Static routing
Correct answer: Router-on-a-stick
Router-on-a-stick uses subinterfaces on the router, each associated with a VLAN, to route traffic between VLANs over one physical trunk link.
Question 2: Which Cisco proprietary protocol dynamically manages VLAN configuration across multiple switches?
- STP
- VTP (VLAN Trunking Protocol) (Correct answer)
- LACP
- CDP
Correct answer: VTP (VLAN Trunking Protocol)
VTP propagates VLAN database changes from a VTP server to all switches in the same VTP domain, reducing manual configuration.
Question 3: What is the native VLAN in 802.1Q trunking?
- The VLAN that carries management traffic only
- The VLAN whose frames are sent untagged across the trunk (Correct answer)
- The highest-priority VLAN on the trunk
- The VLAN assigned to all unused ports
Correct answer: The VLAN whose frames are sent untagged across the trunk
The native VLAN (default VLAN 1) sends and receives untagged frames on 802.1Q trunks; mismatched native VLANs can cause security issues.
Question 4: What does RSTP (802.1w) provide compared to traditional STP (802.1D)?
- Per-VLAN spanning tree instances
- Faster convergence by introducing new port roles and states (Correct answer)
- Load balancing across redundant links
- VLAN pruning across trunk links
Correct answer: Faster convergence by introducing new port roles and states
RSTP reduces convergence time from 30–50 seconds to near-zero by introducing Alternate and Backup port roles and eliminating the Listening state.
Question 5: What is the function of PortFast in Cisco STP implementations?
- It increases STP convergence speed on trunk ports
- It allows access ports connected to end devices to skip STP listening and learning states (Correct answer)
- It elects the root bridge faster
- It enables BPDU filtering on all ports
Correct answer: It allows access ports connected to end devices to skip STP listening and learning states
PortFast immediately transitions an access port to the Forwarding state, avoiding the typical 30-second STP delay for end device connections.
Question 6: Which feature prevents a PortFast-enabled port from causing a topology change if a switch is mistakenly connected to it?
- Root Guard
- BPDU Guard (Correct answer)
- Loop Guard
- UplinkFast
Correct answer: BPDU Guard
BPDU Guard places a PortFast-enabled port into err-disabled state if any BPDU is received, preventing rogue switches from affecting the STP topology.
NE NE Switching 2
What is an inter-VLAN routing method that uses a single trunk link between a router and a switch?