CCNA Network Services and Security Practice Question
Exhibit
R1# show running-config | section interface GigabitEthernet0/0 interface GigabitEthernet0/0 ip address 192.168.1.1 255.255.255.0 ip access-group BLOCK_SERVER in duplex auto speed auto ! R1# show running-config | section ip access-list ip access-list extended BLOCK_SERVER deny tcp any host 203.0.113.5 eq 80 permit ip any any !
You are connected to R1. The network has two routers (R1 and R2) connected via a serial link (S0/0/0). R1's GigabitEthernet0/0 connects to the 192.168.1.0/24 LAN. An extended ACL must be configured on R1 to permit only HTTPS traffic (TCP port 443) from host 192.168.1.10 to server 203.0.113.5 (reachable via R2), and deny all other traffic from the LAN to the server. Currently, the ACL is applied inbound on G0/0 but valid HTTPS traffic is being blocked. Troubleshoot and fix the configuration.
⚠ Common exam trap
Be careful not to assume that an ACL with a permit ip any any will automatically block specific traffic; it actually permits everything. The implicit deny only applies if there is no matching permit statement. Also, pay attention to the specific requirements: the ACL must deny HTTP but permit HTTPS from the host.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ACL is missing an explicit permit statement for HTTPS traffic from host 192.168.1.10 to server 203.0.113.5, and the current permit ip any any allows all traffic, including HTTP, which violates the requirement to deny HTTP.
Valid HTTPS is blocked because the current ACL does not have an effective ACE permitting TCP/443 from 192.168.1.10 to 203.0.113.5; the implicit deny at the end drops that traffic. A reachable `permit ip any any` would allow HTTPS, so if such an ACE appears in the configuration it is not the effective match for this flow. The correct fix adds an explicit permit for TCP 443 from the host to the server, denies HTTP and all other IP traffic from the LAN to the server, and then permits all other IP traffic.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The ACL is missing an explicit permit statement for HTTPS traffic from host 192.168.1.10 to server 203.0.113.5, and the current permit ip any any allows all traffic, including HTTP, which violates the requirement to deny HTTP.
Why this is correct
The correct fix is to add a permit statement for HTTPS (TCP port 443) from the specific host to the server, and then deny HTTP (port 80) from that host to the server, while still allowing other traffic with permit ip any any. The current ACL permits everything, so HTTPS is allowed, but HTTP is also allowed, which should be denied. The problem described says HTTPS is blocked, which suggests the ACL might be misapplied or the implicit deny is blocking HTTPS if the permit ip any any is removed. However, the most likely issue is that the ACL is too permissive and does not meet the requirement to deny HTTP. To fix, the ACL should explicitly permit HTTPS and deny HTTP from that host.
- ✗
The ACL is applied inbound on G0/0, but it should be applied outbound on G0/0 to filter traffic leaving the LAN.
Why it's wrong here
This is incorrect because applying the ACL inbound on G0/0 is appropriate for filtering traffic entering the router from the LAN. The traffic from the LAN to the server enters R1 via G0/0, so inbound application is correct.
- ✗
The ACL should be applied to the serial interface S0/0/0 instead of G0/0 to filter traffic going to R2.
Why it's wrong here
This is incorrect because applying the ACL on S0/0/0 would filter traffic after it has already been routed, but the requirement is to filter traffic from the LAN before it leaves the router. Applying on G0/0 inbound is more efficient and standard.
- ✗
The ACL is missing a deny statement for all other traffic from the LAN to the server, and the permit ip any any allows everything, including unwanted traffic.
Why it's wrong here
This is incorrect because the requirement is to permit only HTTPS and deny all other traffic from the LAN to the server. The current ACL permits all traffic (including HTTPS) but also permits HTTP and other traffic to the server. However, the problem states that HTTPS is blocked, not that HTTP is allowed. So the issue is not that other traffic is allowed, but that HTTPS is blocked. The missing deny statement for other traffic is not the cause of HTTPS being blocked.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓The ACL is missing an explicit permit statement for HTTPS traffic from host 192.168.1.10 to server 203.0.113.5, and the current permit ip any any allows all traffic, including HTTP, which violates the requirement to deny HTTP.Correct answer▾
Why this is correct
The correct fix is to add a permit statement for HTTPS (TCP port 443) from the specific host to the server, and then deny HTTP (port 80) from that host to the server, while still allowing other traffic with permit ip any any. The current ACL permits everything, so HTTPS is allowed, but HTTP is also allowed, which should be denied. The problem described says HTTPS is blocked, which suggests the ACL might be misapplied or the implicit deny is blocking HTTPS if the permit ip any any is removed. However, the most likely issue is that the ACL is too permissive and does not meet the requirement to deny HTTP. To fix, the ACL should explicitly permit HTTPS and deny HTTP from that host.
✗The ACL is applied inbound on G0/0, but it should be applied outbound on G0/0 to filter traffic leaving the LAN.Wrong answer — click to see why▾
Why this is wrong here
The direction of ACL application is correct; inbound on the interface where traffic enters the router is standard for filtering traffic from the LAN.
Why candidates choose this
Candidates often confuse inbound and outbound ACL application, thinking that outbound is needed to filter traffic going out to the server.
✗The ACL should be applied to the serial interface S0/0/0 instead of G0/0 to filter traffic going to R2.Wrong answer — click to see why▾
Why this is wrong here
ACLs should be applied as close to the source as possible to deny traffic early. Applying on the serial interface would still work but is less efficient and not the best practice.
Why candidates choose this
Candidates might think that since the server is reachable via R2, the ACL should be on the serial link to R2.
✗The ACL is missing a deny statement for all other traffic from the LAN to the server, and the permit ip any any allows everything, including unwanted traffic.Wrong answer — click to see why▾
Why this is wrong here
The permit ip any any allows all traffic, so HTTPS should be allowed. The problem says HTTPS is blocked, so the issue must be something else, like a missing explicit permit or a misordering.
Why candidates choose this
Candidates might think that because the ACL does not explicitly permit HTTPS, it is blocked by the implicit deny, but the permit ip any any overrides that.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Related to this question
Learn chapter
Diagnosing DNS Record Issues — A, AAAA, CNAME, MX, NS, and PTR Records
Key term
Access Control List
An Access Control List is a set of rules that decides which traffic is allowed or denied entry to a network or device.
Key term
LAN
Local Area Network — a network confined to a single physical location such as an office, building, or campus.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.