Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
An administrator wants to prevent users from browsing to one specific web server while still allowing them to reach other web destinations. Which ACL design principle is most important here?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
Use the narrowest possible match so only the intended traffic is denied.
This is correct because precise ACL design reduces unintended side effects.
B
Distractor review
Always deny all IP traffic to the destination subnet first.
This is wrong because it may overblock beyond the requirement.
C
Distractor review
Use a standard ACL because destination details never matter.
This is wrong because destination detail matters greatly in this scenario.
D
Distractor review
Place the ACL only where no routing exists.
This is wrong because the key issue here is match precision, not that rule.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is choosing an ACL design that denies all traffic to a destination subnet or using a standard ACL that filters only by source IP address. These approaches are tempting because they seem simpler but result in overblocking, preventing users from accessing other legitimate web servers. Another trap is placing the ACL in a location unrelated to routing or traffic flow, which does not effectively control the targeted traffic. The trap lies in misunderstanding that ACL precision and scope directly impact network usability and security enforcement.
Technical deep dive
How to think about this question
Access Control Lists (ACLs) are fundamental security tools in Cisco networking that filter traffic based on defined criteria such as source/destination IP addresses, protocols, and ports. They enable administrators to permit or deny specific traffic flows, controlling network access and enhancing security. In the context of web traffic, ACLs can be designed to block access to particular web servers by matching destination IP addresses and TCP port 80 or 443 for HTTP/HTTPS traffic. The key to effective ACL design is precision: the ACL must narrowly match only the unwanted traffic to avoid disrupting legitimate communication. For example, denying traffic solely to the specific IP address of the targeted web server and the relevant TCP ports ensures that users can still access other web destinations. Overly broad ACLs, such as denying all traffic to a subnet or using standard ACLs that filter only by source IP, risk blocking more traffic than intended, causing network disruptions. A common exam trap is to apply ACLs too broadly or in the wrong sequence, such as denying all traffic to a destination subnet or using standard ACLs that cannot filter by destination IP. This leads to unintended blocking of legitimate traffic and network outages. Understanding the Cisco ACL processing order and the importance of the narrowest match helps avoid these pitfalls and ensures ACLs enforce security policies without collateral damage.
KKey Concepts to Remember
- ACLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets.
- Extended ACLs allow filtering based on destination IP addresses and TCP/UDP ports, enabling precise control over web traffic access.
- Using the narrowest possible ACL match prevents unintended blocking of legitimate traffic and maintains network usability.
- Standard ACLs filter only by source IP address and cannot control traffic based on destination details, limiting their usefulness for web server blocking.
- Applying ACLs at the correct interface and direction ensures that the intended traffic is filtered effectively without impacting unrelated flows.
- Overly broad ACL rules, such as denying all traffic to a subnet, risk disrupting access to multiple services beyond the targeted web server.
- Cisco ACLs process rules in sequential order, so placing specific deny statements before broader permits is essential for correct behavior.
- ACL design must balance security enforcement with minimizing collateral impact on network communication to avoid operational issues.
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.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
ACLs filter network traffic by matching specific criteria such as source/destination IP addresses, protocols, and ports to permit or deny packets.
What is the correct answer to this question?
The correct answer is: Use the narrowest possible match so only the intended traffic is denied. — The most important principle is to write the ACL as narrowly as possible so it matches only the unwanted traffic and does not overblock unrelated traffic. In practical terms, the rule should target the specific destination and service being denied rather than using a broader deny that unintentionally blocks other communication. This is a precision-and-scope question. Good ACL design is as much about what you avoid blocking as what you intend to block.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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