300-440 Question 213
Single answerYou are troubleshooting a network issue where users are unable to access a sensitive server behind a router. The router is configured with an Access Control List (ACL) to restrict unauthorized access. Upon investigation, you find that the ACL is configured but certain authorized users are still unable to connect. What is the most likely cause of the issue?
- A
The ACL is using the wrong sequence of permit and deny statements.
- B
The ACL is applied in the wrong direction on the router interface.
- C
The ACL is missing the 'established' keyword for stateful filtering.
- D
The ACL is not applied to the correct VLAN.
Show answer and explanation
Correct answer: B
Explanation
When troubleshooting ACL-related issues, it's crucial to verify that the ACL is applied in the correct direction (inbound or outbound) on the appropriate interface. If it's applied incorrectly, traffic will not be evaluated properly, causing connectivity issues even for authorized users. In this scenario, the most likely cause of the issue is that the ACL is applied in the wrong direction.
- A. Incorrect.
While the sequence of permit and deny statements is critical, this option does not explain why authorized users are unable to connect if the ACL itself is valid.
- B. Correct.
If the ACL is applied in the wrong direction (inbound/outbound), traffic from authorized users may not be correctly evaluated, leading to connectivity issues.
- C. Incorrect.
The 'established' keyword is used for stateful filtering of TCP sessions but is not directly related to ACL direction, which is the more likely issue here.
- D. Incorrect.
ACLs are applied to interfaces, not directly to VLANs. This option indicates a misunderstanding of how ACLs function.