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Quick Answer
The answer is that IP Source Guard is typically applied on untrusted access ports to prevent IP spoofing. This is correct because IPSG validates the source IP address of every incoming packet against the DHCP snooping binding database or a manually configured static IP source binding, dropping any packet whose source IP does not match a legitimate entry for that port. On the CCNA 200-301 v2 exam, this concept tests your understanding of Layer 2 security features that work together—DHCP snooping must be enabled first to populate the binding table, and IPSG then enforces those bindings at the port level. A common trap is confusing IPSG with Dynamic ARP Inspection; remember that IPSG filters at Layer 3 (IP), while DAI filters at Layer 2 (ARP). For a quick memory tip, think “IPSG = IP Spoofing Guard” and recall that it only works on untrusted ports where DHCP snooping is active.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 three of the following are characteristics of IP Source Guard on a Cisco switch? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It filters IP traffic based on the source IP address and the DHCP snooping binding.
IP Source Guard (IPSG) filters IP traffic on a per-port basis by validating the source IP address of incoming packets against the DHCP snooping binding database or a manually configured static IP source binding. This prevents IP spoofing attacks by dropping any packet whose source IP does not match a legitimate binding for that port. It is typically enabled on untrusted access ports where DHCP snooping is also active, ensuring that only assigned IP addresses are allowed.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between what IP Source Guard inspects (source IP) versus what Dynamic ARP Inspection inspects (ARP packets), leading candidates to confuse the two or think IPSG checks destination addresses.
Detailed technical explanation
How to think about this question
Under the hood, IP Source Guard leverages the DHCP snooping binding table, which maps a client's MAC address, IP address, VLAN, and port. When a packet arrives on an IPSG-enabled port, the switch performs a lookup in this table; if no matching entry exists (or if the source IP does not match), the packet is dropped. A common real-world scenario is preventing a rogue device from claiming a legitimate host's IP address on a guest network, where IPSG combined with DHCP snooping and DAI provides a robust anti-spoofing defense.
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 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
Questions learners often ask
What does this 200-301 question test?
Network Services and Security — This question tests Network Services and Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: It filters IP traffic based on the source IP address and the DHCP snooping binding. — IP Source Guard (IPSG) filters IP traffic on a per-port basis by validating the source IP address of incoming packets against the DHCP snooping binding database or a manually configured static IP source binding. This prevents IP spoofing attacks by dropping any packet whose source IP does not match a legitimate binding for that port. It is typically enabled on untrusted access ports where DHCP snooping is also active, ensuring that only assigned IP addresses are allowed.
What should I do if I get this 200-301 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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Last reviewed: Jun 11, 2026
This 200-301 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 200-301 exam.
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