The answer is that DNS and MS-SQL traffic are dropped because the BAD_TRAFFIC class explicitly drops them. In a Cisco zone-based firewall configuration, traffic is classified using class maps and then acted upon by a policy map; here, the BAD_TRAFFIC class matches DNS (UDP/53) and MS-SQL (TCP/1433) and applies the drop action, while the class-default uses inspect for GOOD_TRAFFIC. Since the policy processes class matches in order, any traffic hitting BAD_TRAFFIC is dropped before inspection can occur, which explains why users can access HTTP (matched by GOOD_TRAFFIC) but cannot resolve DNS names or reach MS-SQL servers. On the Cisco SCOR 350-701 exam, this scenario tests your understanding of zone-based firewall policy ordering and the explicit drop action—a common trap is assuming that a default inspect action allows all traffic, when in fact explicitly matched classes override the default. Remember the memory tip: “Explicit drop beats default inspect; if it’s in BAD_TRAFFIC, it’s gone static.”
350-701 Security Concepts Practice Question
This 350-701 practice question tests your understanding of security concepts. 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.
Exhibit
policy-map type inspect INSPECT-POLICY
class type inspect BAD_TRAFFIC
drop
class type inspect GOOD_TRAFFIC
inspect
!
class-map type inspect match-any BAD_TRAFFIC
match protocol dns
match protocol ms-sql
!
class-map type inspect match-any GOOD_TRAFFIC
match access-group 100
!
zone security INSIDE
zone security OUTSIDE
zone-pair security ZP-IN-2-OUT source INSIDE destination OUTSIDE
service-policy type inspect INSPECT-POLICY
Refer to the exhibit. A network engineer applies a zone-based firewall policy to a router. Users in the INSIDE zone report they can access HTTP servers on the OUTSIDE zone but cannot resolve DNS names or access MS-SQL servers. What does the policy do to DNS and MS-SQL traffic?
policy-map type inspect INSPECT-POLICY
class type inspect BAD_TRAFFIC
drop
class type inspect GOOD_TRAFFIC
inspect
!
class-map type inspect match-any BAD_TRAFFIC
match protocol dns
match protocol ms-sql
!
class-map type inspect match-any GOOD_TRAFFIC
match access-group 100
!
zone security INSIDE
zone security OUTSIDE
zone-pair security ZP-IN-2-OUT source INSIDE destination OUTSIDE
service-policy type inspect INSPECT-POLICY
A
They are allowed because no 'inspect' action is applied to the class.
Why wrong: The class has a 'drop' action, so they are blocked.
B
They are dropped because the BAD_TRAFFIC class explicitly drops them.
The class BAD_TRAFFIC includes DNS and MS-SQL and applies the drop action.
C
They are inspected and allowed through the firewall.
Why wrong: The policy drops them, not inspects.
D
They are dropped because they do not match the GOOD_TRAFFIC class.
Why wrong: They actually match BAD_TRAFFIC and are explicitly dropped.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
They are dropped because the BAD_TRAFFIC class explicitly drops them.
The correct answer is B because the zone-based firewall policy explicitly defines a class map (BAD_TRAFFIC) that matches DNS (UDP/53) and MS-SQL (TCP/1433) traffic and applies the 'drop' action. Since the policy-map uses a 'class-default' action of 'inspect' for GOOD_TRAFFIC, any traffic not matching GOOD_TRAFFIC but matching BAD_TRAFFIC is dropped before inspection can occur. The users' symptoms confirm that DNS and MS-SQL are being dropped, while HTTP (matched by GOOD_TRAFFIC) is inspected and allowed.
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.
✗
They are allowed because no 'inspect' action is applied to the class.
Why it's wrong here
The class has a 'drop' action, so they are blocked.
✓
They are dropped because the BAD_TRAFFIC class explicitly drops them.
Why this is correct
The class BAD_TRAFFIC includes DNS and MS-SQL and applies the drop action.
Related concept
Read the scenario before looking for a memorised answer.
✗
They are inspected and allowed through the firewall.
Why it's wrong here
The policy drops them, not inspects.
✗
They are dropped because they do not match the GOOD_TRAFFIC class.
Why it's wrong here
They actually match BAD_TRAFFIC and are explicitly dropped.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that 'inspect' in class-default automatically allows all traffic, but the trap here is that explicit 'drop' actions in higher-priority class maps (like BAD_TRAFFIC) override any default inspection, causing candidates to overlook the sequential processing order of class maps in a policy-map.
Detailed technical explanation
How to think about this question
In Cisco zone-based firewall (ZBFW), the policy-map processes class maps in sequential order; if traffic matches BAD_TRAFFIC (e.g., with match protocol dns and match protocol ms-sql), the 'drop' action is applied immediately, and no further inspection occurs. The 'class-default' with 'inspect' only applies to traffic that does not match any explicit class, so DNS and MS-SQL are never evaluated by the GOOD_TRAFFIC class. In real-world deployments, this design is used to explicitly block risky or non-essential services while allowing HTTP/HTTPS, but misordering or missing class maps can lead to unintended drops.
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 practitioner preparing for the 350-701 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Concepts — This question tests Security Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: They are dropped because the BAD_TRAFFIC class explicitly drops them. — The correct answer is B because the zone-based firewall policy explicitly defines a class map (BAD_TRAFFIC) that matches DNS (UDP/53) and MS-SQL (TCP/1433) traffic and applies the 'drop' action. Since the policy-map uses a 'class-default' action of 'inspect' for GOOD_TRAFFIC, any traffic not matching GOOD_TRAFFIC but matching BAD_TRAFFIC is dropped before inspection can occur. The users' symptoms confirm that DNS and MS-SQL are being dropped, while HTTP (matched by GOOD_TRAFFIC) is inspected and allowed.
What should I do if I get this 350-701 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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