Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A network technician is troubleshooting connectivity between two branch offices connected by a site-to-site VPN. The VPN tunnel shows as active and up. Users at Branch A can ping the VPN gateway IP at Branch B successfully, but they cannot access any servers behind the firewall at Branch B. The firewall at Branch B is stateful and its logs show that traffic from Branch A is being dropped. What is the most likely cause?
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
Distractor review
Mismatched encryption algorithms
If encryption algorithms mismatched, the VPN tunnel would not establish successfully; the tunnel is up, so this is not likely.
B
Best answer
Asymmetric routing causing the stateful firewall to drop return traffic
The stateful firewall expects to see both directions of a connection. If traffic from Branch A enters one firewall interface but the return traffic leaves via a different path, the firewall sees the return packet as unsolicited and drops it.
C
Distractor review
Incorrect DNS configuration
While DNS might cause name resolution issues, the traffic is being dropped by the firewall; ping by IP works to the gateway, so DNS is not the problem.
D
Distractor review
MTU mismatch causing fragmentation issues
Fragmentation issues typically cause packet loss or timeouts, but the firewall would log drops due to stateful inspection, not usually due to MTU; MTU issues would not necessarily cause the firewall to drop traffic.
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: Asymmetric routing causing the stateful firewall to drop return traffic — In site-to-site VPNs, if routing is not symmetric (traffic takes a different path back), a stateful firewall at the destination may not have a session entry for the return traffic, causing it to be dropped. This is a common issue with multi-homed networks or when VPN tunnels are not properly routed.
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.
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