Question 1mediummulti select
Full question →mediummulti selectObjective-mapped
A standard numbered ACL is applied close to the destination, but it is blocking traffic from one host while still allowing all other users on the subnet. Which two facts about standard ACLs are relevant in this design?
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
They filter based on source address only
Standard ACLs do not inspect destination addresses or ports.
B
Best answer
They are best placed near the source in most cases
Because they only match source IPs, placing them near the source reduces unwanted broad blocking.
C
Distractor review
They can match TCP and UDP port numbers
That is the role of extended ACLs.
D
Distractor review
They automatically create a permit any at the end
ACLs have an implicit deny at the end.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is assuming that standard ACLs can filter traffic based on destination IP addresses or port numbers. Candidates may incorrectly place standard ACLs near the destination to control traffic more granularly, but since standard ACLs only match source IPs, this placement can block unintended hosts. This misunderstanding leads to unexpected network outages or partial connectivity, especially when trying to block a single host but inadvertently affecting others in the subnet. Recognizing the source-only filtering nature of standard ACLs is essential to avoid this pitfall.
Technical deep dive
How to think about this question
Standard Access Control Lists (ACLs) in Cisco networking filter traffic based solely on the source IP address of packets. Unlike extended ACLs, they do not consider destination IP addresses, protocols, or port numbers. This fundamental design means that standard ACLs apply broad filtering rules that affect all traffic originating from specified source addresses, regardless of where it is headed or what service it uses. Because standard ACLs only match on source IP addresses, best practice dictates placing them as close to the source of traffic as possible. This placement prevents unintended blocking of legitimate traffic from other hosts within the same subnet or network segment. Applying a standard ACL near the destination can inadvertently block traffic from multiple sources, since the ACL cannot differentiate based on destination or service, leading to overly restrictive filtering. A common exam trap involves misplacing standard ACLs near the destination, expecting granular control over traffic. This mistake ignores the ACL’s limitation to source-based filtering and can cause unexpected blocking of hosts. Understanding this behaviour is critical for designing effective ACLs in Cisco environments and avoiding network connectivity issues during CCNA-level configurations.
KKey Concepts to Remember
- Standard ACLs filter traffic exclusively based on the source IP address of packets, ignoring destination addresses and ports.
- Because standard ACLs only inspect source IPs, placing them near the source prevents unintended blocking of other hosts in the subnet.
- Applying a standard ACL near the destination risks blocking more traffic than intended due to its limited filtering criteria.
- Extended ACLs are required to filter traffic based on destination IP addresses, protocols, or TCP/UDP port numbers.
- All ACLs have an implicit deny at the end, meaning any traffic not explicitly permitted is blocked.
- Standard ACLs do not inspect or filter based on TCP or UDP port numbers, limiting their granularity.
- Proper ACL placement is critical to avoid network disruptions and ensure intended traffic flow in Cisco routing environments.
- Misunderstanding standard ACL behaviour can lead to configuration errors and connectivity issues in Cisco networks.
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?
Standard ACLs filter traffic exclusively based on the source IP address of packets, ignoring destination addresses and ports.
What is the correct answer to this question?
The correct answer is: They filter based on source address only — Standard ACLs only match the source IP address. For that reason, they are usually placed near the source so they do not block more traffic than intended.
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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