Quick Answer
The answer is local preference, the BGP attribute used to indicate the degree of preference for a route within an AS and propagated to all iBGP peers. This well-known mandatory attribute influences outbound traffic from the AS by assigning a higher preference to routes with a higher local preference value, which defaults to 100. On the ENCOR 350-401 exam, this concept tests your understanding of BGP path selection within a single autonomous system, often appearing in questions that contrast it with attributes like AS-path or MED, which are not propagated to iBGP peers. A common trap is confusing local preference with MED—remember that local preference is for outbound path selection within your AS, while MED influences inbound traffic from a neighboring AS. For a quick memory tip: think of local preference as the “home team advantage” attribute—higher is better, and it stays inside your AS.
This 350-401 practice question tests your understanding of bgp. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which BGP attribute is used to indicate the degree of preference for a route within an AS and is propagated to all iBGP peers?
Local preference
Correct. Local preference is used within an AS and is propagated to iBGP peers.
MED
Why wrong: Incorrect. MED is used to influence inbound traffic and is not propagated to iBGP peers by default.
Weight
Why wrong: Incorrect. Weight is Cisco-specific and not propagated to any peers.
AS-path
Why wrong: Incorrect. AS-path is used for loop prevention and path selection, not for preference within an AS.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Local preference
Local preference is a well-known mandatory BGP attribute that indicates the degree of preference for a route within an AS. It is propagated to all iBGP peers and, by default, is set to 100. A higher local preference value is preferred when selecting the best path for outbound traffic from the AS.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Local preference
Why this is correct
Correct. Local preference is used within an AS and is propagated to iBGP peers.
Related concept
Read the scenario before looking for a memorised answer.
MED
Why it's wrong here
Incorrect. MED is used to influence inbound traffic and is not propagated to iBGP peers by default.
Weight
Why it's wrong here
Incorrect. Weight is Cisco-specific and not propagated to any peers.
AS-path
Why it's wrong here
Incorrect. AS-path is used for loop prevention and path selection, not for preference within an AS.
Common exam traps
Cisco often tests the distinction between attributes that are propagated within an AS (local preference) versus those that are not (weight), or those that influence inbound versus outbound traffic (MED vs. local preference).
Detailed technical explanation
Under the hood, local preference is carried in the BGP update message as a 4-byte unsigned integer (RFC 4271). In a real-world scenario, an ISP might set a higher local preference for routes learned from a primary upstream provider to ensure that outbound traffic prefers that link over a backup, and this preference is consistently applied across all routers in the AS via iBGP propagation.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
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FAQ
BGP — This question tests BGP — Read the scenario before looking for a memorised answer..
The correct answer is: Local preference — Local preference is a well-known mandatory BGP attribute that indicates the degree of preference for a route within an AS. It is propagated to all iBGP peers and, by default, is set to 100. A higher local preference value is preferred when selecting the best path for outbound traffic from the AS.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.
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