350-401 Question #1039: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. A network engineer issues the debug command while troubleshooting a network issue. What does the output confirm?

Options

• AACL 100 is tracking ICMP traffic from 10.1.1.1 destined for 1.1.1.1.
• BACL100 is tracking all traffic from 10.1.1.1 destined for 1.1.1.1.
• CACL100 is tracking ICMP traffic from Serial1/0 destined for Serial3/0.
• DACL100 is tracking ICMP traffic from 1.1.1.1 destined for 10.1.1.1.

Explanation

The debug ip icmp command displays information about ICMP packets and, when combined with ACL logging, can confirm specific traffic flows evaluated by an ACL.

Common mistakes.

• A. Without the exhibit, it's impossible to confirm the specific direction or source/destination, but this option implies a different traffic flow than the correct answer.
• B. ACL100 would typically track specific types of traffic based on its configuration, not 'all traffic' between two hosts, especially with debug ip icmp only showing ICMP.
• C. ACLs track IP addresses, not interfaces like Serial1/0 or Serial3/0, although traffic might traverse those interfaces. The debug output would show IP addresses.

Concept tested. Debugging ICMP and ACLs

Reference. https://www.cisco.com/c/en/us/td/docs/ios/12_2/debug/command/reference/drfioscr.html

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