1. What additional information is contained in the 12-bit extended system ID of a BPDU?
MAC address
VLAN ID
IP address
port ID
2. During the implementation of Spanning Tree Protocol, all switches are rebooted by the network administrator. What is the first step of the spanning-tree election process?
Each switch with a lower root ID than its neighbor will not send BPDUs.
All the switches send out BPDUs advertising themselves as the root bridge.
Each switch determines the best path to forward traffic.
Each switch determines what port to block to prevent a loop from occurring.
3. Which STP port role is adopted by a switch port if there is no other port with a lower cost to the root bridge?
designated port
root port
alternate
disabled port
Explanation: The root port is the port with the lowest cost to reach the root bridge.
4. Which two concepts relate to a switch port that is intended to have only end devices attached and intended never to be used to connect to another switch? (Choose two.)
bridge ID
edge port
extended system ID
PortFast
PVST+
5. Which three components are combined to form a bridge ID?
extended system ID
cost
IP address
bridge priority
MAC address
port ID
Explanation: The three components that are combined to form a bridge ID are bridge priority, extended system ID, and MAC address.
6. Match the STP protocol with the correct description. (Not all options are used.)
CCNA-2-v7-Modules 5 – 6 Redundant Networks Exam 6
7. In which two port states does a switch learn MAC addresses and process BPDUs in a PVST network? (Choose two.)
disabled
forwarding
listening
blocking
learning
Explanation: Switches learn MAC addresses at the learning and forwarding port states. They receive and process BPDUs at the blocking, listening, learning, and forwarding port states.
8. If no bridge priority is configured in PVST, which criteria is considered when electing the root bridge?
lowest MAC address
lowest IP address
highest IP address
highest MAC address
Explanation: Only one switch can be the root bridge for a VLAN. The root bridge is the switch with the lowest BID. The BID is determined by priority and the MAC address. If no priority is configured then all switches use the default priority and the election of the root bridge will be based on the lowest MAC address.
9. Match the spanning-tree feature with the protocol type. (Not all options are used.)
CCNA-2-v7-Modules 5 – 6 Redundant Networks Exam 9
Explanation: MST is the Cisco implementation of MSTP (IEEE 802.1s).
10. When the show spanning-tree vlan 33 command is issued on a switch, three ports are shown in the forwarding state. In which two port roles could these interfaces function while in the forwarding state? (Choose two.)
alternate
designated
disabled
blocked
root
Explanation: The role of each of the three ports will be either designated port or root port. Ports in the disabled state are administratively disabled. Ports in the blocking state are alternate ports.
11. What is the function of STP in a scalable network?
It decreases the size of the failure domain to contain the impact of failures.
It protects the edge of the enterprise network from malicious activity.
It combines multiple switch trunk links to act as one logical link for increased bandwidth.
It disables redundant paths to eliminate Layer 2 loops.
Explanation: STP is an important component in a scalable network because it allows redundant physical connections between Layer 2 devices to be implemented without creating Layer 2 loops. STP prevents Layer 2 loops from forming by disabling interfaces on Layer 2 devices when they would create a loop.
12. What is a characteristic of spanning tree?
It is enabled by default on Cisco switches.
It is used to discover information about an adjacent Cisco device.
It has a TTL mechanism that works at Layer 2.
It prevents propagation of Layer 2 broadcast frames.
Explanation: Spanning tree does work at Layer 2 on Ethernet-based networks and is enabled by default, but it does not have a TTL mechanism. Spanning tree exists because Layer 2 frames do not have a TTL mechanism. Layer 2 frames are still broadcast when spanning tree is enabled, but the frames can only be transmitted through a single path through the Layer 2 network that was created by spanning tree. Cisco Discovery Protocol (CDP) is used to discover information about an adjacent Cisco device.
13. Which spanning tree standard supports only one root bridge so that traffic from all VLANs flows over the same path?
PVST+
802.1D
MST
Rapid PVST
Explanation: MST is the Cisco implementation of MSTP, an IEEE standard protocol that provides up to 16 instances of RSTP. PVST+ provides a separate 802.1D spanning-tree instance for each VLAN that is configured in the network. 802.1D is the original STP standard defined by the IEEE and allows for only one root bridge for all VLANs. 802.1w, or RSTP, provides faster convergence but still uses only one STP instance for all VLANs.
14. What is the purpose of the Spanning Tree Protocol (STP)?
creates smaller collision domains
prevents routing loops on a router
prevents Layer 2 loops
allows Cisco devices to exchange routing table updates
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