This CISSP practice question tests your understanding of communication and network security. 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 company uses BGP to exchange routes with its ISP. To prevent prefix hijacking, which mechanism should be implemented?
BGP MD5 authentication
Why wrong: Authenticates BGP peers but does not validate prefix origin.
BGP community values
Why wrong: Used for tagging routes, not for preventing hijacking.
RPKI
Validates the origin AS of prefixes, mitigating hijacking.
AS-path filtering
Why wrong: Filters based on AS path but does not validate prefix ownership.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
RPKI
RPKI (Resource Public Key Infrastructure) is the correct mechanism because it cryptographically validates the origin AS of a BGP route announcement, preventing prefix hijacking by ensuring that only the legitimate owner of an IP prefix can announce it. Unlike other options, RPKI provides a trust anchor based on the IP address allocation hierarchy, making it the only solution that directly addresses the root cause of hijacking—unauthorized origin AS claims.
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.
BGP MD5 authentication
Why it's wrong here
Authenticates BGP peers but does not validate prefix origin.
BGP community values
Why it's wrong here
Used for tagging routes, not for preventing hijacking.
RPKI
Why this is correct
Validates the origin AS of prefixes, mitigating hijacking.
Related concept
Read the scenario before looking for a memorised answer.
AS-path filtering
Why it's wrong here
Filters based on AS path but does not validate prefix ownership.
Common exam traps
ISC2 often tests BGP MD5 authentication as a security measure, but the trap here is confusing session-level authentication (MD5) with route-level validation (RPKI), leading candidates to choose A because they think 'authentication' covers route integrity, when it only protects the BGP session itself.
Detailed technical explanation
RPKI works by creating a chain of trust from the five Regional Internet Registries (RIRs) down to ISPs and end users, who sign Route Origin Authorizations (ROAs) that bind an IP prefix to an authorized origin AS. BGP routers then perform RPKI-based route validation using the 'rpki-validate' command (e.g., in Cisco IOS) to classify routes as Valid, Invalid, or NotFound, with Invalid routes being dropped or given a low local preference. A subtle behavior is that RPKI does not prevent path hijacking (where an attacker prepends a valid AS to a false prefix), but it does stop origin hijacking, which is the most common and damaging form of prefix hijacking.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
What to study next
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FAQ
Communication and Network Security — This question tests Communication and Network Security — Read the scenario before looking for a memorised answer..
The correct answer is: RPKI — RPKI (Resource Public Key Infrastructure) is the correct mechanism because it cryptographically validates the origin AS of a BGP route announcement, preventing prefix hijacking by ensuring that only the legitimate owner of an IP prefix can announce it. Unlike other options, RPKI provides a trust anchor based on the IP address allocation hierarchy, making it the only solution that directly addresses the root cause of hijacking—unauthorized origin AS claims.
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 30, 2026
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