The answer is that two active ISAKMP SAs between the same peers indicate a configuration error, not a redundancy feature. This occurs because ISAKMP is designed to maintain a single security association per peer pair; multiple SAs, especially with differing encryption algorithms like DES and 3DES, suggest that multiple ISAKMP policies are matching or that aggressive mode is creating duplicates. On the Cisco CCNP ENARSI 300-410 exam, this output tests your ability to distinguish between normal IPsec operation and misconfiguration, often appearing as a trap where candidates mistakenly view multiple SAs as load balancing or failover. Remember that ISAKMP SAs are not redundant—they are negotiated once per phase 1 exchange, so duplicates always point to policy overlap or aggressive mode issues. A useful memory tip: “One peer, one SA—two means trouble in the negotiation play.”
300-410 IPsec Site-to-Site VPN Practice Question
This 300-410 practice question tests your understanding of ipsec site-to-site vpn. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network engineer runs the following command to troubleshoot an IPsec Site-to-Site VPN issue:
R1# show crypto isakmp sa detail
IPv4 Crypto ISAKMP SA
C-id Local Remote I-VRF Status Encr Hash Auth DH Lifetime Cap.
1001 192.168.1.1 192.168.2.2 ACTIVE des sha pre 2 23:59:21
1002 192.168.1.1 192.168.2.2 ACTIVE 3des sha pre 2 23:58:15
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
There are two active ISAKMP SAs between the peers, which suggests a configuration error such as multiple ISAKMP policies or aggressive mode issues.
The output shows two active ISAKMP SAs between the same peers (192.168.1.1 and 192.168.2.2) with different encryption algorithms (DES and 3DES). Under normal operation, only one ISAKMP SA should exist per peer pair. Having multiple SAs indicates a configuration error, such as multiple ISAKMP policies that both match, or aggressive mode causing duplicate SAs. This is not a sign of redundancy; ISAKMP SAs are not redundant by design.
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.
✗
The IPsec VPN is functioning correctly with two redundant ISAKMP SAs.
Why it's wrong here
Multiple ISAKMP SAs between same peers is not normal and indicates a problem.
✓
There are two active ISAKMP SAs between the peers, which suggests a configuration error such as multiple ISAKMP policies or aggressive mode issues.
Why this is correct
Having two SAs is abnormal; it often results from misconfigured policies or aggressive mode causing duplicate SAs.
Related concept
Read the scenario before looking for a memorised answer.
✗
The ISAKMP SA is using DES encryption, which is weak and should be upgraded.
Why it's wrong here
While DES is weak, the primary issue is the duplicate SAs, not the encryption strength.
✗
The ISAKMP SA lifetime is about 24 hours, which is the default.
Why it's wrong here
The lifetime is default, but the main issue is the duplicate SAs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that multiple active ISAKMP SAs between the same peers are normal or provide redundancy, when in fact they indicate a configuration error that can break the VPN tunnel.
Detailed technical explanation
How to think about this question
ISAKMP (IKE) Phase 1 establishes a single SA per peer pair to protect subsequent IKE negotiations. When multiple ISAKMP policies are configured, the peers negotiate to select one matching policy; if multiple policies match (e.g., due to aggressive mode or misordered proposals), duplicate SAs can be created. This can lead to instability, as each SA may have different parameters, and the VPN may flap or fail to establish IPsec SAs correctly. The 'show crypto isakmp sa detail' command is the primary tool to detect this issue.
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 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.
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: There are two active ISAKMP SAs between the peers, which suggests a configuration error such as multiple ISAKMP policies or aggressive mode issues. — The output shows two active ISAKMP SAs between the same peers (192.168.1.1 and 192.168.2.2) with different encryption algorithms (DES and 3DES). Under normal operation, only one ISAKMP SA should exist per peer pair. Having multiple SAs indicates a configuration error, such as multiple ISAKMP policies that both match, or aggressive mode causing duplicate SAs. This is not a sign of redundancy; ISAKMP SAs are not redundant by design.
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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