ACL Security Operations & Monitoring 3

Question 1

A network engineer needs to verify whether ACL traffic filtering is causing an application outage. Which two tools should be used first?

Accepted Answer

show ip access-lists and debug ip packet detail

Answer

'show ip access-lists' reveals hit counters to confirm if an ACL is matching traffic, and 'debug ip packet detail' shows real-time packet processing decisions.

Question 2

What does a zero hit count on an ACL deny rule likely indicate during troubleshooting?

Accepted Answer

Traffic matching that rule has not been seen, or the ACL is not applied correctly

Answer

A zero hit count means either no traffic matching that ACE has arrived, or the ACL is not applied to the correct interface or direction.

Question 3

An administrator applies a strict ACL on a router and immediately loses SSH access to the device. What ACL design mistake most likely caused this?

Accepted Answer

A deny rule blocked management traffic before a permit rule allowed it

Answer

Placing a broad deny rule above the management traffic permit rule in the ACL will block SSH before it can be permitted, locking out the administrator.

Question 4

Which command clears ACL hit counters on a Cisco router without removing the ACL from the interface?

Accepted Answer

clear ip access-list counters ACL_NAME

Answer

'clear ip access-list counters' resets hit counters for the specified ACL while leaving the ACL configuration and interface binding intact.

Question 5

A security team uses NetFlow data alongside ACL logs. What gap does NetFlow fill that ACL logs alone cannot provide?

Accepted Answer

NetFlow captures permitted traffic volume and flow duration for baseline analysis

Answer

NetFlow records traffic statistics for all flows (including permitted ones), giving visibility into normal and abnormal traffic volumes that ACL logs (which only record matches) cannot provide alone.

(ACL) Access Control Lists Practice Test

(ACL) Access Control Lists Practice Test

ACL Security Operations & Monitoring 3