Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Which statement best describes why PortFast is usually appropriate on a user-facing access port but not on a normal switch-to-switch uplink?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
Because PortFast is intended for edge ports and a normal uplink participates in the spanning-tree topology.
This is correct because PortFast is designed for endpoint-facing ports, not typical inter-switch links.
B
Distractor review
Because PortFast can be used only on routers.
This is wrong because PortFast is a switching feature, not a router-only feature.
C
Distractor review
Because switch-to-switch links cannot forward traffic.
This is wrong because uplinks obviously do forward traffic and are critical to switching topology.
D
Distractor review
Because PortFast automatically enables NAT on access ports.
This is wrong because PortFast has nothing to do with NAT.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is selecting an answer that suggests PortFast can be used on any port to speed up connectivity, including switch-to-switch uplinks. This is incorrect because PortFast disables the STP states that prevent loops, and uplinks must participate fully in STP to maintain a loop-free topology. Candidates may confuse PortFast’s purpose and think it is a general speed-up feature rather than a specialized function for edge ports. Misunderstanding this leads to incorrect assumptions about network stability and STP operation.
Technical deep dive
How to think about this question
PortFast is a Cisco switch feature that allows a switch port to bypass the usual Spanning Tree Protocol (STP) listening and learning states and immediately transition to the forwarding state. This behavior is critical for edge ports connected directly to end devices like PCs, printers, or IP phones, where rapid network access is needed without the delay caused by STP convergence. STP normally prevents loops by blocking redundant paths, but this process introduces a delay of about 30 to 50 seconds before a port forwards traffic. The decision to enable PortFast is based on the port's role in the network topology. Ports connected to end devices are considered edge ports and can safely use PortFast because they do not create switching loops. In contrast, switch-to-switch uplinks participate in the spanning-tree topology and must undergo the normal STP process to detect and prevent loops. Enabling PortFast on these uplinks risks creating bridging loops, which can cause broadcast storms and network instability. A common exam trap is assuming PortFast can be enabled on any port to speed up connectivity. While PortFast accelerates port activation, enabling it on switch-to-switch links bypasses critical STP loop prevention mechanisms. In practical networks, PortFast is strictly limited to edge ports, and Cisco best practices recommend disabling it on all trunk or uplink ports to maintain network stability and proper STP operation.
KKey Concepts to Remember
- PortFast immediately transitions an edge port to forwarding state, bypassing the standard STP listening and learning states to reduce startup delay for end devices.
- STP prevents switching loops by blocking redundant paths, and normal switch-to-switch uplinks must participate fully in STP to maintain loop-free topology.
- PortFast is intended only for ports connected directly to end devices, not for switch-to-switch uplinks that form part of the spanning-tree topology.
- Enabling PortFast on a switch-to-switch uplink can cause bridging loops because it disables STP’s loop detection and blocking mechanisms on that link.
- Cisco best practices require PortFast to be enabled only on access ports facing hosts to improve network convergence without compromising topology stability.
- Switch ports configured with PortFast do not send or process BPDU packets normally, which is why they should not be used on links between switches.
- A port with PortFast enabled transitions to forwarding state immediately upon link-up, which helps reduce DHCP delays and improves user experience on access ports.
- Normal uplink ports participate in STP by exchanging BPDUs to elect root bridges and determine port roles, which is essential for loop prevention.
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 an edge port to forwarding state, bypassing the standard STP listening and learning states to reduce startup delay for end devices.
What is the correct answer to this question?
The correct answer is: Because PortFast is intended for edge ports and a normal uplink participates in the spanning-tree topology. — PortFast is appropriate on a user-facing access port because it speeds an edge port into forwarding without waiting through the normal STP transition. In practical terms, that improves startup behavior for hosts such as PCs and printers. On a normal switch-to-switch uplink, however, the link participates in spanning-tree topology decisions, so treating it like a simple edge port can introduce risk. This is a standard access-layer design principle. PortFast is for endpoints, not ordinary infrastructure uplinks.
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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