The answer is an ACL to define interesting traffic and an ISAKMP policy. The ACL is essential because it identifies which traffic should be encrypted and sent through the VPN tunnel, acting as a traffic selector that triggers the IPsec process. The ISAKMP policy is equally critical as it defines the Phase 1 parameters—such as encryption algorithm, authentication method, Diffie-Hellman group, and lifetime—without which the router cannot establish the secure management tunnel needed to negotiate IPsec Security Associations. On the Cisco SCOR 350-701 exam, this concept tests your understanding of the foundational building blocks for site-to-site IPsec VPNs; a common trap is confusing the ISAKMP policy with the IPsec transform set, which governs Phase 2. Remember that Phase 1 is about securing the management channel, while Phase 2 protects the data. A helpful memory tip: "ISAKMP builds the tunnel; the ACL decides what goes through it."
350-701 Network Security Practice Question
This 350-701 practice question tests your understanding of network security. 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.
Which TWO of the following are required to configure a site-to-site IPsec VPN on a Cisco IOS router?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ISAKMP policy
ISAKMP (Internet Security Association and Key Management Protocol) policy is required to define the parameters for Phase 1 of an IPsecVPN, including encryption, authentication, Diffie-Hellman group, and lifetime. Without an ISAKMP policy, the router cannot establish the secure management tunnel needed to negotiate IPsec Security Associations (SAs).
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.
✓
ISAKMP policy
Why this is correct
ISAKMP policy is required for IKE phase 1 negotiation.
Related concept
Read the scenario before looking for a memorised answer.
✓
ACL to define interesting traffic
Why this is correct
The crypto ACL selects the traffic to be encrypted.
Related concept
Read the scenario before looking for a memorised answer.
✗
NAT exemption for VPN traffic
Why it's wrong here
NAT exemption is only needed if NAT is configured; not always required.
✗
AAA new-model
Why it's wrong here
AAA new-model is not a prerequisite for site-to-site VPN.
✗
DHCP pool for remote clients
Why it's wrong here
DHCP pool is for remote access VPN clients, not site-to-site.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between mandatory and optional components, so the trap here is that candidates may think NAT exemption or AAA is always required, when in fact they are only needed in specific scenarios (e.g., overlapping subnets or centralized authentication).
Detailed technical explanation
How to think about this question
In a site-to-site IPsecVPN, ISAKMP (IKEv1 or IKEv2) negotiates Phase 1 using UDP port 500, establishing a secure channel for Phase 2 IPsec SA negotiation. The ACL for interesting traffic (crypto map ACL) triggers IPsec encryption by matching traffic that should be protected, and without it, no traffic is encrypted even if ISAKMP is configured. A common subtlety is that the ACL must be mirrored on both peers for successful SA negotiation.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Network Security — This question tests Network Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: ISAKMP policy — ISAKMP (Internet Security Association and Key Management Protocol) policy is required to define the parameters for Phase 1 of an IPsec VPN, including encryption, authentication, Diffie-Hellman group, and lifetime. Without an ISAKMP policy, the router cannot establish the secure management tunnel needed to negotiate IPsec Security Associations (SAs).
What should I do if I get this 350-701 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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