The answer is that nothing is missing; the configuration is complete and correct for a site-to-site IPsec VPN. This is because the configuration properly establishes both IKE Phase 1 (ISAKMP policy with AES-256, pre-shared key, DH group 14, and 86400-second lifetime) and IKE Phase 2 (IPsec transform set with AES-256 and SHA-HMAC), binds them via the crypto map to the peer at 192.168.1.2, and applies that map to the outgoing interface. The access-list 101 correctly defines interesting traffic between 10.1.1.0/24 and 10.2.2.0/24, and since the peer is directly connected on the same subnet, no additional route to the remote LAN is required—IPsec encrypts traffic matched by the ACL, not by routing tables. On the Cisco CCNP ENARSI 300-410 exam, this question tests your ability to spot a complete IPsec VPN configuration without falling for the common trap of thinking a static route to the remote network is mandatory. A helpful memory tip: “ACL defines what to encrypt, routing only needs to reach the peer’s public IP.”
300-410 IPsec Site-to-Site VPN Practice Question
This 300-410 practice question tests your understanding of ipsec site-to-site vpn. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Examine this configuration on router R1:
crypto isakmp policy 10
encryption aes 256
authentication pre-share
group 14
lifetime 86400
!
All necessary components: ISAKMP policy, key, transform set, crypto map with peer and ACL, and interface application.
B
A route to the remote LAN 10.2.2.0/24 is missing.
Why wrong: Routing is separate from IPsec; the tunnel can be established without a route, but traffic may not be forwarded correctly. However, the question asks what is missing for the tunnel to work, and IPsec itself does not require a route.
C
The ISAKMP policy needs a 'lifetime' value.
Why wrong: A lifetime is already configured (86400).
D
The transform set should include 'mode transport' for site-to-site.
Why wrong: Tunnel mode is correct for site-to-site VPNs.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Nothing is missing; the configuration is correct.
The configuration is complete for a site-to-site IPsecVPN. ISAKMP policy 10 specifies AES-256 encryption, pre-shared key authentication, Diffie-Hellman group 14, and a lifetime of 86400 seconds (the default is 86400, so explicitly setting it is fine). The crypto map CMAP binds the transform set TSET (AES-256, SHA-HMAC) to peer 192.168.1.2 and matches interesting traffic via access-list 101 (10.1.1.0/24 to 10.2.2.0/24). The interface GigabitEthernet0/1 applies the crypto map. A route to the remote LAN is not required because IPsec encrypts traffic based on the crypto ACL; routing only needs to reach the peer's public IP (192.168.1.2), which is directly connected on the same subnet.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Nothing is missing; the configuration is correct.
Why this is correct
All necessary components: ISAKMP policy, key, transform set, crypto map with peer and ACL, and interface application.
Related concept
Read the scenario before looking for a memorised answer.
✗
A route to the remote LAN 10.2.2.0/24 is missing.
Why it's wrong here
Routing is separate from IPsec; the tunnel can be established without a route, but traffic may not be forwarded correctly. However, the question asks what is missing for the tunnel to work, and IPsec itself does not require a route.
✗
The ISAKMP policy needs a 'lifetime' value.
Why it's wrong here
A lifetime is already configured (86400).
✗
The transform set should include 'mode transport' for site-to-site.
Why it's wrong here
Tunnel mode is correct for site-to-site VPNs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a route to the remote LAN is required for IPsec to work, but in reality, the crypto ACL handles traffic selection, and only a route to the peer's public IP is needed.
Detailed technical explanation
How to think about this question
In site-to-site IPsec, the crypto ACL defines the traffic that triggers encryption, but the router does not need a route to the remote LAN because the decrypted packets are forwarded based on the routing table of the remote router. The ISAKMP lifetime of 86400 seconds is the default, so explicitly configuring it is redundant but not an error. The 'mode tunnel' in the transform set encapsulates the entire original IP packet with a new IP header, which is standard for site-to-site VPNs; 'mode transport' only encrypts the payload and is typically used with GRE tunnels or direct host connections.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
IPsec Site-to-Site VPN — This question tests IPsec Site-to-Site VPN — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Nothing is missing; the configuration is correct. — The configuration is complete for a site-to-site IPsec VPN. ISAKMP policy 10 specifies AES-256 encryption, pre-shared key authentication, Diffie-Hellman group 14, and a lifetime of 86400 seconds (the default is 86400, so explicitly setting it is fine). The crypto map CMAP binds the transform set TSET (AES-256, SHA-HMAC) to peer 192.168.1.2 and matches interesting traffic via access-list 101 (10.1.1.0/24 to 10.2.2.0/24). The interface GigabitEthernet0/1 applies the crypto map. A route to the remote LAN is not required because IPsec encrypts traffic based on the crypto ACL; routing only needs to reach the peer's public IP (192.168.1.2), which is directly connected on the same subnet.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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