The correct answer is that the IPsec tunnel is established only when traffic from 10.1.1.0/24 to 10.2.2.0/24 triggers it. This happens because the crypto map references access-list 101 via the match address command, which defines the interesting traffic that initiates IKEv1 phase 1 and phase 2 negotiations. Until a packet matching that ACL is sent, no ISAKMP or IPsec security associations are created—the tunnel remains dormant. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of how crypto maps use ACLs to trigger tunnel establishment, a common point of confusion where candidates mistakenly assume the tunnel is always active. A frequent trap is thinking the crypto isakmp key or transform-set alone builds the tunnel, but without matching traffic, nothing happens. Memory tip: “No match, no catch”—the ACL is the trigger, not the tunnel itself.
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.
Given the following partial configuration on router R1:
crypto isakmp policy 10
encryption aes 256
authentication pre-share
group 14
lifetime 86400
!
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
IPsec tunnel is established when traffic from 10.1.1.0/24 to 10.2.2.0/24 triggers it.
Option A is correct because the configuration uses a crypto map with 'match address 101' referencing an ACL that permits traffic from 10.1.1.0/24 to 10.2.2.0/24. This triggers IPsec SA negotiation via ISAKMP (IKEv1) only when interesting traffic is detected. The tunnel is established dynamically upon matching traffic, which is the standard behavior for a site-to-site VPN using a crypto map.
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.
✓
IPsec tunnel is established when traffic from 10.1.1.0/24 to 10.2.2.0/24 triggers it.
Why this is correct
ACL 101 defines interesting traffic; once matched, IKE and IPsec negotiations begin.
Related concept
Read the scenario before looking for a memorised answer.
✗
The tunnel will only be established if the peer initiates first.
Why it's wrong here
The configuration allows either side to initiate, as long as interesting traffic is detected.
✗
The transform set uses AES 256 with MD5 authentication, which is incorrect.
Why it's wrong here
The transform set uses esp-sha-hmac, which is SHA, not MD5.
✗
ISAKMP lifetime is set to 86400 seconds, which is too short for a site-to-site VPN.
Why it's wrong here
86400 seconds (24 hours) is a common default and acceptable for site-to-site VPNs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a crypto map tunnel requires the peer to initiate first, but the default behavior is that the local router initiates when interesting traffic is sent, unless 'responder-only' is configured.
Detailed technical explanation
How to think about this question
Under the hood, IKEv1 (ISAKMP) uses UDP port 500 for Phase 1 negotiation, and the 'group 14' command specifies a Diffie-Hellman group providing 2048-bit key strength. The 'lifetime 86400' applies to the ISAKMP SA, after which rekeying occurs; IPsec SA lifetimes are configured separately under the transform set or crypto map. In real-world scenarios, mismatched ACLs or missing 'isakmp key' entries are common misconfigurations that prevent tunnel establishment.
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: IPsec tunnel is established when traffic from 10.1.1.0/24 to 10.2.2.0/24 triggers it. — Option A is correct because the configuration uses a crypto map with 'match address 101' referencing an ACL that permits traffic from 10.1.1.0/24 to 10.2.2.0/24. This triggers IPsec SA negotiation via ISAKMP (IKEv1) only when interesting traffic is detected. The tunnel is established dynamically upon matching traffic, which is the standard behavior for a site-to-site VPN using a crypto map.
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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Question Discussion
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