20+ practice questions focused on IPsec Site-to-Site VPN — one of the most tested topics on the Cisco CCNP ENARSI 300-410 exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start IPsec Site-to-Site VPN PracticeA network engineer is troubleshooting an IPsec site-to-site VPN between two routers. The tunnel interface is up/up, but traffic from the local LAN to the remote LAN is not passing. The engineer checks the crypto map and sees it is applied to the outside interface. What is the most likely cause of the traffic failure?
Explanation: The tunnel interface being up/up indicates the GRE tunnel is operational, but traffic may still fail if the crypto map is not correctly triggering IPsec encryption for the actual data traffic. The most common cause is a missing or incorrect access list in the crypto map that defines interesting traffic.
A network engineer is troubleshooting an IPsec site-to-site VPN where the tunnel is not coming up. The engineer runs 'show crypto isakmp sa' and sees no active IKE SAs. The peer IP address is correctly configured. What should the engineer check first?
Explanation: The absence of IKE SAs indicates that IKE phase 1 negotiation has not started or failed. The first step is to verify that the routers can reach each other at the IP layer, as a connectivity issue will prevent any IKE exchange.
A network engineer is troubleshooting an IPsec site-to-site VPN between two Cisco routers. The tunnel is up, but traffic intermittently drops. The engineer notices that the 'show crypto ipsec sa' output shows the packet counters incrementing for both encrypt and decrypt, but the 'pkts encaps failed' counter is also increasing. What is the most likely cause?
Explanation: The 'pkts encaps failed' counter indicates that the router is unable to encrypt packets that should be encrypted. This typically happens when the crypto map's access list matches traffic, but the route to the remote LAN points out an interface that does not have the crypto map applied, causing the router to try to send the packet without encryption.
A network engineer is troubleshooting an IPsec site-to-site VPN where the tunnel is up but traffic from the remote LAN to the local LAN is not working. The engineer pings from the remote router to the local LAN IP and it succeeds. However, pings from a host on the remote LAN to a host on the local LAN fail. What is the most likely cause?
Explanation: The symptom indicates that the VPN tunnel is working for traffic sourced from the router itself, but not for traffic from the remote LAN. This is typically caused by a missing route on the local router for the remote LAN subnet, or a missing route on the remote router for the local LAN subnet, preventing the return traffic from being routed correctly.
A network engineer is troubleshooting an IPsec site-to-site VPN that uses a GRE tunnel over IPsec. The GRE tunnel is up/up, but the routing protocol (EIGRP) running over the GRE tunnel is not forming an adjacency. The engineer checks the tunnel configuration and sees that the tunnel source and destination are correct. What is the most likely cause?
Explanation: For a GRE over IPsec tunnel, the GRE tunnel must be protected by the crypto map. If the crypto map is applied to the physical interface but the GRE tunnel traffic is not matched by the crypto map's access list, the GRE packets will be sent unencrypted and the remote router will drop them, preventing the routing protocol from forming an adjacency.
+15 more IPsec Site-to-Site VPN questions available
Practice all IPsec Site-to-Site VPN questions1. Baseline your knowledge
Start with 10 questions to gauge your current understanding of IPsec Site-to-Site VPN. This tells you whether you need a concept refresher or just practice.
2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
IPsec Site-to-Site VPN questions on the 300-410 frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. IPsec Site-to-Site VPN is tested as part of the Cisco CCNP ENARSI 300-410 blueprint. Practicing with targeted IPsec Site-to-Site VPN questions ensures you can handle any format or difficulty that appears.
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Difficulty is subjective, but IPsec Site-to-Site VPN is a high-priority exam concept tested in multiple ways — direct recall, scenario analysis, and command-output interpretation. Consistent practice is the best way to build confidence.
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