Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
A security auditor discovers that an unauthorized switch has been connected to an access port in the wiring closet. The rogue switch caused a network loop and disrupted connectivity. Which security feature, if enabled on the access port, would have prevented this by disabling the port when a BPDU is received?
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
BPDU guard
Correct. BPDU guard disables a port that receives a BPDU, effectively blocking unauthorized switches.
B
Distractor review
Root guard
Incorrect. Root guard prevents a port from becoming a root bridge but does not block BPDU reception entirely.
C
Distractor review
Loop guard
Incorrect. Loop guard prevents alternate ports from forwarding if BPDUs stop being received, but it does not disable the port upon receiving BPDUs.
D
Distractor review
UDLD
Incorrect. UDLD detects unidirectional links but does not prevent BPDU-related loops from rogue switches.
Common exam trap
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Technical deep dive
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
- Static NAT maps one inside address to one outside address.
- PAT allows many inside hosts to share one public address using ports.
- Inside local and inside global describe the private and translated addresses.
- NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
- Identify inside and outside interfaces first.
- Check whether the scenario needs static NAT, dynamic NAT or PAT.
- Do not confuse NAT matching ACLs with normal packet-filtering intent.
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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 network engineer needs to connect two switches located 400 meters apart. The cable run includes high electromagnetic interference from nearby machinery. The engineer decides to use fiber optic cabling. Which transceiver type and fiber combination should be used to ensure the link reaches 400 meters while remaining cost-effective?
Question 2
A network engineer is designing a new switched network and needs to ensure that broadcast traffic from one department does not reach another department's workstations. The engineer plans to use VLANs. Which of the following must be configured on the switches to isolate broadcast domains as intended?
Question 3
A security engineer is configuring a site-to-site VPN between two branch offices. The requirement is to encrypt all traffic between the two networks using IPsec. Which IPsec mode should be used to encrypt the entire IP packet including the original header?
Question 4
A network administrator is connecting two switches to increase bandwidth and provide redundancy. Which technology should be used to combine multiple physical links into a single logical link?
Question 5
A network administrator is experiencing issues where unauthorized devices are offering IP addresses to clients, causing connectivity problems. Which security feature should be enabled on switches to prevent this?
Question 6
A network administrator is troubleshooting a connectivity issue and suspects the problem is related to the physical cabling. At which layer of the OSI model should the administrator begin their investigation?
FAQ
Questions learners often ask
What does this N10-009 question test?
Static NAT maps one inside address to one outside address.
What is the correct answer to this question?
The correct answer is: BPDU guard — BPDU guard is a security feature that disables a port configured with PortFast if it receives any BPDU (Bridge Protocol Data Unit). This prevents rogue switches from being connected and causing loops. Root guard prevents a port from becoming the root bridge, loop guard prevents alternate ports from forwarding in the absence of BPDUs, and UDLD detects unidirectional links. BPDU guard directly addresses the described attack.
What should I do if I get this N10-009 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
Discussion
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