The answer is the Multi-Exit Discriminator (MED). This BGP attribute is used to influence inbound traffic from a neighboring autonomous system when multiple entry points exist between the two networks. A lower MED value is preferred, meaning an AS can advertise a specific path as more desirable for incoming traffic, effectively telling the neighbor, “Please enter here rather than through my other connection.” On the CompTIA Network+ N10-009 exam, this concept tests your understanding of path selection and traffic engineering between ASes. A common trap is confusing MED with Local Preference—remember that MED influences inbound traffic from a neighbor, while Local Preference influences outbound traffic from your own AS. For a quick memory tip, think “MED = My Entry Door,” as it helps you decide which door (entry point) the neighbor should use to reach your network.
N10-009 Networking Concepts Practice Question
This N10-009 practice question tests your understanding of networking concepts. 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.
A network administrator is configuring BGP between two autonomous systems. Which BGP attribute is primarily used to influence inbound traffic to a particular AS?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MED (Multi-Exit Discriminator)
The Multi-Exit Discriminator (MED) is a BGP attribute used to influence inbound traffic from a neighboring AS when multiple entry points exist. A lower MED value is preferred, allowing an AS to advertise to its neighbor which path should be used to reach it, thereby influencing traffic entering the local AS.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
AS_PATH
Why it's wrong here
AS_PATH influences outbound traffic by affecting path selection for routes advertised.
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Next Hop
Why it's wrong here
Next hop is used for reachability, not for inbound traffic influence.
✗
Local Preference
Why it's wrong here
Local preference influences outbound traffic selection from the router's AS.
✓
MED (Multi-Exit Discriminator)
Why this is correct
The MED attribute is used to suggest to a neighboring AS the preferred path for inbound traffic when multiple entry points exist.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is confusing MED with Local Preference: candidates often pick Local Preference because it is a well-known attribute for path selection, but it influences outbound traffic from the local AS, not inbound traffic from a neighboring AS.
Detailed technical explanation
How to think about this question
MED is an optional non-transitive attribute exchanged between eBGP peers, typically set on routes advertised to a neighbor AS to indicate the preferred ingress point. In a scenario with dual-homed connections to an ISP, setting a lower MED on one link can steer incoming traffic away from a congested path. MED values are compared only if the paths come from the same neighboring AS (RFC 4271), and Cisco routers compare MED across different ASes only if the 'bgp always-compare-med' command is configured.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this N10-009 question in full detail.
Networking Concepts — This question tests Networking Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: MED (Multi-Exit Discriminator) — The Multi-Exit Discriminator (MED) is a BGP attribute used to influence inbound traffic from a neighboring AS when multiple entry points exist. A lower MED value is preferred, allowing an AS to advertise to its neighbor which path should be used to reach it, thereby influencing traffic entering the local AS.
What should I do if I get this N10-009 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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