Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
An administrator wants to allow HTTPS traffic from a source subnet to a server but deny all Telnet traffic from that same subnet to the same server. Which ACL capability is required to express that policy accurately?
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
An extended ACL that can match protocol and destination port information
This is correct because the requirement depends on protocol/port-level filtering.
B
Distractor review
A standard ACL because source matching is enough
This is wrong because the policy must distinguish HTTPS from Telnet.
C
Distractor review
A wildcard mask with all zeros only
This is wrong because wildcard details alone do not provide protocol/port granularity.
D
Distractor review
A wireless SSID ACL
This is wrong because the question is about IP traffic filtering, not WLAN naming or association policy.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is selecting a standard ACL to enforce policies that require filtering by protocol or port number. Standard ACLs only filter by source IP address and cannot distinguish between different types of traffic like HTTPS and Telnet. This leads to incorrect assumptions that standard ACLs can block Telnet while allowing HTTPS from the same subnet. The trap lies in overlooking the need for protocol and port-level filtering, which only extended ACLs provide. Candidates must remember that without extended ACLs, the router cannot differentiate traffic based on application-layer details, causing the policy to fail.
Technical deep dive
How to think about this question
Access Control Lists (ACLs) are fundamental tools in Cisco networking used to filter traffic based on defined criteria. Standard ACLs filter traffic solely based on source IP addresses, which limits their ability to differentiate traffic types. Extended ACLs, however, provide granular control by allowing filtering based on multiple parameters including source and destination IP addresses, protocol types (such as TCP or UDP), and specific port numbers. This capability is essential when policies require distinguishing between different application traffic, such as HTTPS and Telnet. In the scenario where an administrator wants to permit HTTPS traffic (TCP port 443) while denying Telnet traffic (TCP port 23) from the same source subnet to a server, an extended ACL is necessary. The extended ACL can explicitly match the TCP protocol and the destination port number, enabling precise control over which traffic is allowed or denied. Standard ACLs cannot differentiate traffic by port or protocol, making them insufficient for this requirement. A common exam trap is assuming that standard ACLs can enforce policies based on application types or ports, which they cannot. Extended ACLs are the correct choice because they provide the necessary filtering granularity. Practically, using extended ACLs ensures that only the intended traffic (HTTPS) reaches the server, while unwanted traffic (Telnet) is blocked, enhancing network security and compliance with access policies.
KKey Concepts to Remember
- Extended ACLs allow filtering based on source and destination IP addresses, protocols, and port numbers, enabling precise traffic control.
- Standard ACLs filter traffic only by source IP address and cannot differentiate between protocols or ports, limiting their use for application-specific policies.
- An extended ACL can explicitly permit HTTPS traffic by matching TCP protocol and destination port 443 while denying Telnet traffic on TCP port 23 from the same source subnet.
- Cisco routers process ACL entries in sequential order, stopping at the first match, so rule order is critical in extended ACL configuration.
- Using extended ACLs improves network security by allowing administrators to enforce policies that distinguish between different application traffic types.
- ACLs applied inbound or outbound on interfaces control traffic flow and can prevent unauthorized access to network resources based on defined criteria.
- Misusing standard ACLs for protocol or port filtering is a common mistake that leads to ineffective access control and potential security risks.
- Extended ACLs are essential in scenarios requiring granular control over traffic, such as permitting HTTPS while denying Telnet from the same source to the same destination.
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?
Extended ACLs allow filtering based on source and destination IP addresses, protocols, and port numbers, enabling precise traffic control.
What is the correct answer to this question?
The correct answer is: An extended ACL that can match protocol and destination port information — The policy requires extended ACL capability because it must distinguish traffic by protocol and destination port, not just by source address. In practical terms, the rule needs to treat TCP port 443 differently from TCP port 23 even though the source and destination networks are the same. A standard ACL is too limited for that. This question is about matching precision. When the policy depends on protocol and port, extended ACLs are the right tool.
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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