350-501 Question #35: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. A network engineer is implementing a BGP routing policy. Which effect of this configuration is true?

Options

• AAll traffic that matches acl10 is allowed without any change to its local-preference
• BAll traffic that matches acl10 is dropped without any change to its local-preference
• CIf traffic matches acl10, it is allowed and its local-preference is set to 300
• DAll traffic is assigned a local-preference of 30O regardless of its destination

Explanation

In Cisco IOS XR route-policy, an explicit set local-preference command within an if block, without a subsequent pass or accept action, will result in the matched traffic being allowed but without the local-preference change being applied.

Common mistakes.

• B. The policy implicitly allows routes that match the if condition when no explicit drop is specified, so traffic will not be dropped.
• C. This is incorrect because, without an explicit pass or accept command after the set local-preference 300, the local-preference value is not actually applied to the routes, even though they match the acl10 condition.
• D. The set local-preference 300 action is conditioned on traffic matching acl10; therefore, it will not be applied to all traffic regardless of its destination.

Concept tested. IOS XR route-policy 'set' action behavior

Reference. https://www.cisco.com/c/en/us/td/docs/iosxr/asr9000/routing/611/b-routing-611-asr9k-cg/b-routing-611-asr9k-cg_chapter_0100.html

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