Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A network engineer has successfully established an IPsec site-to-site VPN tunnel between a branch office (10.0.1.0/24) and the main office (192.168.1.0/24). The tunnel status shows as active, and both sides can ping each other's tunnel interface IP addresses. However, users at the branch office cannot ping the main office server at 192.168.1.10, and the main office cannot ping the branch office server at 10.0.1.10. The firewall rules on both sides permit IPsec traffic and all internal traffic. What should the engineer check NEXT?
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
Verify routing entries on both routers to ensure the remote internal subnets are reachable via the tunnel.
Both routers need to have routes pointing to the remote internal subnets (e.g., 192.168.1.0/24 and 10.0.1.0/24) with the tunnel interface as the next hop. Without these routes, traffic from internal hosts will not be directed into the tunnel.
B
Distractor review
Check the IPsec security associations for encryption algorithm mismatch.
If the tunnel is active and both sides can ping tunnel IPs, the IPsec parameters are correctly negotiated. An algorithm mismatch would prevent the tunnel from establishing.
C
Distractor review
Disable the firewall on the internal interfaces temporarily.
The firewall rules already permit traffic. Disabling firewalls is not a best practice and would not resolve a routing issue.
D
Distractor review
Regenerate the pre-shared key on both sides.
Regenerating the PSK is unnecessary because the tunnel is already established. The PSK is only used during initial authentication.
Common exam trap
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Technical deep dive
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
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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?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: Verify routing entries on both routers to ensure the remote internal subnets are reachable via the tunnel. — Even if the IPsec tunnel is up and endpoints can ping the tunnel IPs, internal hosts may not be able to communicate if routing is not properly configured. The engineer must ensure that both routers have routes to the remote internal networks, either statically or dynamically, so that packets from internal hosts are sent through the tunnel. Additionally, Network Address Translation (NAT) policies should be checked to ensure they are not translating the internal traffic that should be encrypted.
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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