The route from Peer A is preferred because BGP route selection local preference is evaluated before AS path length. Local preference is the second step in the BGP best-path selection algorithm, after the weight attribute, and a higher value is always preferred. Peer A’s local preference of 150 outweighs Peer B’s 100, making the AS path length of 3 versus 2 irrelevant in this comparison. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this concept frequently appears in troubleshooting scenarios where engineers mistakenly assume a shorter AS path always wins. The common trap is forgetting that local preference is an administrative weight applied within the AS and overrides path length entirely. Remember the mnemonic: “We Love Oranges AS Oranges” — Weight, Local Preference, Originate, AS path, Origin — and local preference always beats AS path.
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A service provider is troubleshooting BGP route selection between two eBGP peers. The router receives a prefix from Peer A with local preference 150 and AS path length 3. From Peer B, the same prefix has local preference 100 and AS path length 2. Which route will be preferred?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The route from Peer A because local preference is higher.
BGP selects the route with highest local preference first. Peer A has local preference 150, which is higher than Peer B's 100, so Peer A's route is preferred regardless of AS path length.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The route from Peer A because it has a higher weight.
Why it's wrong here
Weight is not mentioned; local preference is the decisive factor here.
✓
The route from Peer A because local preference is higher.
Why this is correct
Local preference is the first tiebreaker after weight; higher value wins.
Related concept
Static NAT maps one inside address to one outside address.
✗
Both routes are equally preferred and will be used for load balancing.
Why it's wrong here
BGP selects only one best path unless multipath is configured.
✗
The route from Peer B because AS path is shorter.
Why it's wrong here
AS path length is considered only if local preference is equal.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-501 NAT questions on configuration and troubleshooting.
Networking — This question tests Networking — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The route from Peer A because local preference is higher. — BGP selects the route with highest local preference first. Peer A has local preference 150, which is higher than Peer B's 100, so Peer A's route is preferred regardless of AS path length.
What should I do if I get this 350-501 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-501 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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