Question 1mediummatching
Full question →Match each ACL-related term to its most accurate description.
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mediummatchingObjective-mapped
Match each ACL-related term to its most accurate description.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming that ACLs permit all traffic not explicitly denied. In reality, every ACL ends with an implicit deny that blocks all unmatched traffic, which can cause unexpected connectivity issues. Another common mistake is confusing standard and extended ACLs; standard ACLs only filter by source IP, so expecting them to filter by destination or protocol leads to errors. Misunderstanding wildcard masks also causes ACLs to match incorrect IP addresses, either permitting unauthorized traffic or blocking legitimate packets. Recognizing these nuances is critical to avoid selecting incorrect answers on the exam.
Technical deep dive
How to think about this question
Access Control Lists (ACLs) are fundamental security tools in Cisco networking that control traffic flow by filtering packets based on defined criteria. Standard ACLs filter traffic solely based on the source IP address, making them simpler but less granular. Extended ACLs provide more detailed filtering by considering source and destination IP addresses, protocols (such as TCP, UDP, ICMP), and port numbers, enabling precise control over network traffic. Wildcard masks are used in ACLs to specify which bits of an IP address should be matched exactly and which can vary, allowing flexible address matching. When processing packets, ACLs evaluate entries sequentially from top to bottom. If a packet matches an ACL entry, the corresponding permit or deny action is applied immediately. If no entries match, an implicit deny at the end of every ACL silently blocks the packet. This implicit deny is not explicitly configured but is critical to understand because it can cause unexpected traffic drops if no permit statements match. Proper ACL design requires careful ordering of statements and understanding of wildcard masks to ensure intended traffic is allowed or blocked. A common exam trap involves confusing standard and extended ACL capabilities or overlooking the implicit deny rule. Candidates may assume that an ACL permits all traffic not explicitly denied, but the implicit deny denies all unmatched traffic by default. Additionally, misunderstanding wildcard masks can lead to incorrect ACL entries that either over-permit or over-block traffic. In practical networks, ACLs must be carefully tested and applied to the correct interfaces and directions to enforce security policies effectively without disrupting legitimate traffic.
KKey Concepts to Remember
- A standard ACL filters traffic based solely on the source IP address, providing basic filtering capabilities.
- An extended ACL filters traffic based on source and destination IP addresses, protocols, and port numbers for granular control.
- Wildcard masks in ACLs specify which bits of an IP address must match exactly and which bits can vary, enabling flexible matching.
- ACLs process entries sequentially and apply the first matching permit or deny action to the packet.
- Every ACL has an implicit deny at the end that blocks all traffic not explicitly permitted by preceding entries.
- Proper ACL design requires ordering statements carefully to ensure intended traffic is permitted before the implicit deny.
- Extended ACLs allow filtering by protocol type, such as TCP, UDP, or ICMP, which standard ACLs cannot do.
- Applying ACLs on the correct interface and direction is essential to enforce security policies without unintended traffic disruption.
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?
A standard ACL filters traffic based solely on the source IP address, providing basic filtering capabilities.
What exam trap should I watch out for?
Common exam trap: answer the scenario, not the keyword: A frequent exam trap is assuming that ACLs permit all traffic not explicitly denied. In reality, every ACL ends with an implicit deny that blocks all unmatched traffic, which can cause unexpected connectivity issues. Another common mistake is confusing standard and extended ACLs; standard ACLs only filter by source IP, so expecting them to filter by destination or protocol leads to errors. Misunderstanding wildcard masks also causes ACLs to match incorrect IP addresses, either permitting unauthorized traffic or blocking legitimate packets. Recognizing these nuances is critical to avoid selecting incorrect answers on the exam.
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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