Question 1mediummatching
Full question →Match each switchport or STP feature to its most accurate purpose.
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mediummatchingObjective-mapped
Match each switchport or STP feature to its most accurate purpose.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is confusing the purposes of PortFast and BPDU Guard in STP configurations. Candidates might incorrectly think PortFast disables a port upon receiving BPDUs, but PortFast actually forces a port into forwarding state immediately. BPDU Guard is the feature that disables a port if it receives a BPDU, protecting the network from potential loops. Another trap is mixing up Root Guard with Port Security; Root Guard prevents a port from becoming a root port under superior BPDU conditions, while Port Security limits MAC addresses on a port. Misunderstanding these distinctions can lead to incorrect answers.
Technical deep dive
How to think about this question
Spanning Tree Protocol (STP) is essential for preventing Layer 2 loops in Ethernet networks. PortFast is a Cisco feature that immediately transitions a switchport configured as an edge port into the forwarding state, bypassing the usual listening and learning states. This reduces the time it takes for devices connected to that port to start communicating, which is critical for end devices like workstations or servers that do not create loops. However, PortFast should only be enabled on ports connected to end devices, not other switches. BPDU Guard complements PortFast by protecting the network from accidental topology changes. When BPDU Guard is enabled on a PortFast-enabled port, if any Bridge Protocol Data Units (BPDUs) are received on that port, the port is immediately shut down (put into an error-disabled state). This prevents rogue switches or misconfigurations from causing STP recalculations or loops. Root Guard, on the other hand, is used on ports where the network administrator wants to enforce the current root bridge placement. If a superior BPDU is received on a Root Guard-enabled port, that port is put into a root-inconsistent state, preventing it from becoming a root port and thus preserving the intended STP topology. Port Security is a separate feature that controls which MAC addresses can send traffic on a switchport. It limits the number of MAC addresses learned and can restrict access to known devices, enhancing security by preventing unauthorized devices from connecting. Unlike STP features, Port Security does not affect the STP topology but protects the network from MAC flooding or unauthorized access. Understanding these distinct purposes helps network engineers design stable and secure Layer 2 networks and avoid misconfigurations that can cause outages or security breaches.
KKey Concepts to Remember
- PortFast immediately transitions a switchport into the forwarding state to speed up connectivity for end devices without causing STP topology changes.
- BPDU Guard disables a PortFast-enabled switchport if any BPDUs are received, protecting the network from accidental or malicious topology changes.
- Root Guard prevents a switchport from becoming a root port by blocking superior BPDUs, maintaining the designated root bridge in the STP topology.
- Port Security limits the number of MAC addresses on a switchport and controls which devices can access the network through that port.
- PortFast should only be enabled on edge ports connected to end devices to avoid introducing Layer 2 loops in the network.
- BPDU Guard is critical for protecting edge ports from rogue switches that might send BPDUs and disrupt STP stability.
- Root Guard enforces STP topology by ensuring that the root bridge placement remains consistent and prevents unauthorized root bridge elections.
- Port Security enhances network security by preventing unauthorized devices from connecting through a switchport based on MAC address restrictions.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
PortFast immediately transitions a switchport into the forwarding state to speed up connectivity for end devices without causing STP topology changes.
What exam trap should I watch out for?
Common exam trap: answer the scenario, not the keyword: A common exam trap is confusing the purposes of PortFast and BPDU Guard in STP configurations. Candidates might incorrectly think PortFast disables a port upon receiving BPDUs, but PortFast actually forces a port into forwarding state immediately. BPDU Guard is the feature that disables a port if it receives a BPDU, protecting the network from potential loops. Another trap is mixing up Root Guard with Port Security; Root Guard prevents a port from becoming a root port under superior BPDU conditions, while Port Security limits MAC addresses on a port. Misunderstanding these distinctions can lead to incorrect answers.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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