Quick Answer
The answer is 86400 seconds, or 24 hours, which is the default ISAKMP lifetime for IPsec on Cisco IOS routers. This value is set by default in the `crypto isakmp policy` and governs how long the IKE phase 1 security association remains valid before requiring re-authentication and a new Diffie-Hellman exchange. The 24-hour window is designed to balance security with performance, as shorter lifetimes increase CPU overhead from frequent key exchanges, while longer lifetimes risk exposing the tunnel to prolonged attacks. On the Cisco CCNP ENARSI 300-410 exam, this concept often appears in questions about IPsec site-to-site VPN configuration, where a common trap is confusing the ISAKMP lifetime with the shorter IPsec (IKE phase 2) lifetime, which defaults to 3600 seconds (one hour). A useful memory tip: think of ISAKMP as the "long-term relationship" lasting a full day (24 hours), while IPsec SAs are the "short-term sessions" that refresh every hour.
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.
In IPsec site-to-site VPN, what is the default lifetime for ISAKMP (IKE phase 1) security associations on Cisco IOS routers?
3600 seconds (1 hour)
Why wrong: 3600 seconds is the default for IPsec (phase 2) SA, not ISAKMP.
86400 seconds (24 hours)
This is the Cisco default for ISAKMP lifetime.
28800 seconds (8 hours)
Why wrong: This is not a standard default; 86400 is the correct value.
1800 seconds (30 minutes)
Why wrong: This is too short and not the default.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
86400 seconds (24 hours)
The default lifetime for ISAKMP (IKE phase 1) security associations on Cisco IOS routers is 86400 seconds (24 hours). This is defined in the Cisco IOS default configuration for the `crypto isakmp policy` and is the recommended value to balance security and performance by reducing the frequency of re-authentication and Diffie-Hellman key exchanges.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
3600 seconds (1 hour)
Why it's wrong here
3600 seconds is the default for IPsec (phase 2) SA, not ISAKMP.
86400 seconds (24 hours)
Why this is correct
This is the Cisco default for ISAKMP lifetime.
Related concept
Read the scenario before looking for a memorised answer.
28800 seconds (8 hours)
Why it's wrong here
This is not a standard default; 86400 is the correct value.
1800 seconds (30 minutes)
Why it's wrong here
This is too short and not the default.
Common exam traps
Cisco often tests the distinction between IKE phase 1 and IPsec phase 2 default lifetimes, so the trap here is confusing the 86400-second (24-hour) default for ISAKMP with the 3600-second (1-hour) default for IPsec SAs.
Detailed technical explanation
The ISAKMP (IKE phase 1) SA lifetime is negotiated during the main mode or aggressive mode exchange; the peer with the shorter lifetime wins. Under the hood, the SA is stored in the `show crypto isakmp sa` output and its expiration triggers a new Diffie-Hellman exchange, which is computationally expensive. In real-world deployments, a 24-hour lifetime is standard to avoid frequent rekeying over WAN links, but some organizations reduce it to 8 hours for stricter security compliance.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
IPsec Site-to-Site VPN — study guide chapter
Learn the concepts, then practise the questions
IPsec Site-to-Site VPN practice questions
Targeted practice on this topic area only
All 300-410 questions
2,152 questions across all exam domains
Cisco CCNP ENARSI 300-410 study guide
Full concept coverage aligned to exam objectives
300-410 practice test guide
How to use practice tests most effectively before exam day
Related practice questions
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
Practise 300-410 questions linked to Layer 3 Technologies.
Practise 300-410 questions linked to EIGRP Troubleshooting.
Practise 300-410 questions linked to OSPF Troubleshooting (v2/v3).
Practise 300-410 questions linked to BGP Troubleshooting.
Practise 300-410 questions linked to Route Redistribution.
Practise 300-410 questions linked to Policy-Based Routing (PBR).
Practise 300-410 questions linked to VRF-Lite.
Practise 300-410 questions linked to Route Maps and Route Filtering.
Practise 300-410 questions linked to Administrative Distance.
Practise 300-410 questions linked to Route Summarization.
Practise 300-410 questions linked to Bidirectional Forwarding Detection (BFD).
Practise 300-410 questions linked to VPN Technologies.
Practice this exam
Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.
FAQ
IPsec Site-to-Site VPN — This question tests IPsec Site-to-Site VPN — Read the scenario before looking for a memorised answer..
The correct answer is: 86400 seconds (24 hours) — The default lifetime for ISAKMP (IKE phase 1) security associations on Cisco IOS routers is 86400 seconds (24 hours). This is defined in the Cisco IOS default configuration for the `crypto isakmp policy` and is the recommended value to balance security and performance by reducing the frequency of re-authentication and Diffie-Hellman key exchanges.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 24, 2026
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.