350-501 Question #97: Real Exam Question with Answer & Explanation

Question

An engineer working for telecommunication company with an employee id: 3715 15 021 needs to secure the LAN network using a prefix list. Which best practice should the engineer follow when he implements a prefix list?

Options

• AAn engineer must use non sequential sequence numbers in the prefix list so that he can insert
• BThe final entry in a prefix list must be /32
• CAn engineer must identity the prefix list with a number only
• DAn engineer must include only the prefixes for which he needs to log activity.

Explanation

When implementing a prefix list, it is best practice to use non-sequential sequence numbers to allow for easier insertion of new entries between existing ones without reconfiguring the entire list.

Common mistakes.

• B. The final entry in a prefix list is typically an implicit permit or deny all, not necessarily a /32 for all final entries.
• C. Prefix lists can be identified by both numbers and names, with named prefix lists often preferred for clarity and ease of management.
• D. Prefix lists are primarily used for filtering routes based on their network prefixes, not solely for logging activity; logging is an optional feature.

Concept tested. Prefix list best practices and sequence numbers

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_pi/configuration/15-mt/iri-pi-15-mt-book/iri-pi-prefix-lists.html

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