Cisco ENCOR Lan Switches 2 — Questions and Answers
Question 1: Which Spanning Tree Protocol feature allows a port to immediately transition to the forwarding state when connected to an end device?
- UplinkFast
- BackboneFast
- PortFast (Correct answer)
- RootGuard
Correct answer: PortFast
PortFast skips the listening and learning STP states so end-device ports forward immediately without waiting the standard 30 seconds.
Question 2: A switch receives a frame with a destination MAC address not found in its CAM table. What action does it take?
- Drops the frame silently
- Sends an ARP request
- Floods the frame out all ports except the ingress port (Correct answer)
- Forwards the frame to the default gateway
Correct answer: Floods the frame out all ports except the ingress port
When a destination MAC is unknown, the switch floods the frame out all ports in the same VLAN except the port it arrived on — this is called unknown unicast flooding.
Question 3: Which EtherChannel negotiation protocol is Cisco proprietary?
- LACP
- PAgP (Correct answer)
- LLDP
- RSTP
Correct answer: PAgP
Port Aggregation Protocol (PAgP) is Cisco's proprietary protocol for negotiating EtherChannel link bundles, whereas LACP is the IEEE 802.3ad standard.
Question 4: In PVST+, which switch is elected as the root bridge for each VLAN?
- The switch with the highest bridge priority
- The switch with the lowest bridge ID (priority + MAC) (Correct answer)
- The switch with the most ports active
- The switch with the highest MAC address
Correct answer: The switch with the lowest bridge ID (priority + MAC)
The root bridge is elected as the switch with the lowest bridge ID, which is the combination of the bridge priority and MAC address.
Question 5: Which command configures a switch port as an 802.1Q trunk that allows all VLANs?
- switchport mode access
- switchport trunk encapsulation dot1q followed by switchport mode trunk (Correct answer)
- switchport nonegotiate
- switchport trunk native vlan 1
Correct answer: switchport trunk encapsulation dot1q followed by switchport mode trunk
You must first set the encapsulation to dot1q, then set the mode to trunk; without both commands the port does not become an active 802.1Q trunk.
Question 6: What is the default STP port cost for a 1 Gbps link using the IEEE short path cost method?
- 4 (Correct answer)
- 19
- 100
- 200
Correct answer: 4
Using the IEEE 802.1D short (16-bit) path cost method, a 1 Gbps link has a default cost of 4.
Question 7: Which switch security feature limits the number of MAC addresses learned on a port and disables the port on violation?
- Dynamic ARP Inspection
- DHCP Snooping
- Port Security (Correct answer)
- Storm Control
Correct answer: Port Security
Port Security allows you to restrict the number of valid MAC addresses on a port and choose a violation action such as shutdown.
Cisco ENCOR Lan Switches 2
Which Spanning Tree Protocol feature allows a port to immediately transition to the forwarding state when connected to an end device?