The answer is to create a second contract from App to Web with the same filter, applying App as consumer and Web as provider. This is necessary because ACI contracts are unidirectional by default; despite the filter permitting TCP 8080 from Web to App, ACI does not perform stateful inspection for TCP connections, so return traffic from App to Web requires an explicit contract in the opposite direction. On the Cisco DCCOR / CCNP Data Center Core 350-601 exam, this scenario tests your understanding that ACI treats all traffic as stateless at the contract level, a common trap where engineers assume stateful behavior similar to a firewall. The key distinction is that ACI’s contract model enforces policy per direction, not per flow. Memory tip: “ACI contracts are one-way streets—if you need a round trip, build two roads.”
350-601 Security Practice Question
This 350-601 practice question tests your understanding of 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.
In a Cisco Application Centric Infrastructure (ACI) fabric, a tenant has two EPGs: Web and App. A contract is created between Web (consumer) and App (provider) with a filter that permits TCP port 8080 (the only port used by the application). However, traffic from App to Web is failing. The application requires bidirectional communication: Web initiates requests to App on TCP 8080, and App responds on the same connection (stateful). The engineer verifies that the filter is correctly applied and that both EPGs are in the same VRF. The contract is applied in the direction Web -> App. What is the most efficient way to resolve this issue without compromising security?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a second contract from App to Web with the same filter, and apply it to App as consumer and Web as provider.
In Cisco ACI, contracts are unidirectional by default. Even though the filter permits TCP 8080 from Web to App, the return traffic from App to Web is not implicitly allowed because ACI does not perform stateful inspection for TCP connections; it relies on explicit contract rules for each direction. Option C correctly creates a second contract from App (consumer) to Web (provider) with the same filter, allowing the bidirectional communication required for the application's stateful TCP session without over-permitting.
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.
✗
Verify that no higher-priority contract is overriding; if not, the issue is elsewhere.
Why it's wrong here
While possible, the most common cause is the unidirectional nature of contracts.
✗
Set the contract to 'allow any' between the EPGs to bypass filtering.
Why it's wrong here
This would remove all security, which is not acceptable.
✓
Create a second contract from App to Web with the same filter, and apply it to App as consumer and Web as provider.
Why this is correct
This adds the reverse direction explicitly, allowing return traffic.
Related concept
Read the scenario before looking for a memorised answer.
✗
Modify the existing filter to allow TCP 8080 from App to Web as well.
Why it's wrong here
Filter direction does not change contract direction; the contract still only applies from Web to App.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that ACI contracts are stateful like a firewall, leading candidates to assume return traffic is automatically allowed; the trap here is that ACI requires explicit contracts for each direction, even for TCP connections.
Detailed technical explanation
How to think about this question
ACI contracts operate at Layer 4 and are strictly directional; a contract from consumer to provider only permits traffic in that direction, and return traffic must be explicitly permitted by a separate contract in the opposite direction. This differs from traditional firewalls that track TCP state and automatically allow return packets. In real-world deployments, applications with bidirectional flows (e.g., database queries, API calls) require paired contracts to ensure both request and response paths are open, while maintaining granular security.
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.
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.
Security — This question tests Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a second contract from App to Web with the same filter, and apply it to App as consumer and Web as provider. — In Cisco ACI, contracts are unidirectional by default. Even though the filter permits TCP 8080 from Web to App, the return traffic from App to Web is not implicitly allowed because ACI does not perform stateful inspection for TCP connections; it relies on explicit contract rules for each direction. Option C correctly creates a second contract from App (consumer) to Web (provider) with the same filter, allowing the bidirectional communication required for the application's stateful TCP session without over-permitting.
What should I do if I get this 350-601 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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