The correct answer is Option A, which configures the extended ACL named BRANCH_IN with the precise permit statements for HTTP and ICMP echo-reply, then applies it inbound on GigabitEthernet0/0. This is correct because an extended ACL evaluates both source and destination IP addresses along with protocol-specific fields; the first permit statement restricts TCP port 80 traffic from the 192.168.1.0/24 network to the web server at 203.0.113.10, while the second permit statement uses the echo-reply keyword to allow only ICMP Type 0 responses, not all ICMP types. On the CCNA 200-301 v2 exam, this task tests your ability to match ACL placement with traffic flow direction—a common trap is applying the ACL outbound on the internal interface, which would not filter traffic leaving toward the WAN, or using “any any” for ICMP, which permits unnecessary echo requests and other types. Remember the memory tip: “Inbound on the inside, filter what arrives; outbound on the outside, filter what departs.” For ICMP, always specify echo-reply if you only want responses to pings, not the pings themselves.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Network Topology
You are connected to R1, a branch router. Configure an extended ACL named BRANCH_IN that permits only HTTP (TCP port 80) traffic from the internal network 192.168.1.0/24 to the web server at 203.0.113.10, and permits ICMP echo-reply from any source to any destination. Apply the ACL inbound on the interface facing the internal network. Then verify that only the specified traffic is allowed.
R1# show running-config | section interface
interface GigabitEthernet0/0
description Link to Internal LAN
ip address 192.168.1.1 255.255.255.0
duplex auto
speed auto
!
interface GigabitEthernet0/1
description Link to ISP
ip address 203.0.113.2 255.255.255.252
duplex auto
speed auto
!
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
A
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in
This configuration correctly defines the extended ACL with the required permit statements and applies it inbound on the internal-facing interface. The first permit allows HTTP from the internal subnet to the web server, and the second permit allows ICMP echo-reply from any source. The implicit deny at the end blocks all other traffic.
B
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN out
Why wrong: This is incorrect because the ACL is applied outbound instead of inbound on the internal-facing interface. The task specifically requires the ACL to be applied inbound on the interface facing the internal network.
C
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in
Why wrong: This is incorrect because the ICMP permit statement allows all ICMP types, not just echo-reply. The task specifically requires only ICMP echo-reply to be permitted.
D
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in
!
interface GigabitEthernet0/1
ip access-group BRANCH_IN in
Why wrong: This is incorrect because the ACL is applied to two interfaces, including the external-facing interface (G0/1). The task only requires the ACL to be applied inbound on the internal-facing interface.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in
Option A is correct because it creates an extended ACL that permits TCP port 80 from the internal 192.168.1.0/24 to the web server 203.0.113.10 and permits only ICMP echo-reply, then applies it inbound on the internal interface G0/0, matching the requirement. Option B is wrong because the ACL is applied outbound on G0/0, but traffic from internal hosts to the web server exits via the WAN interface (G0/1), not G0/0. Option C is wrong because it permits all ICMP (any any) instead of only echo-reply, allowing unnecessary ICMP traffic. Option D is wrong because it applies the ACL inbound on both G0/0 and G0/1; applying it on G0/1 would incorrectly filter inbound traffic from the ISP, potentially blocking the web server's responses.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in
Why this is correct
This configuration correctly defines the extended ACL with the required permit statements and applies it inbound on the internal-facing interface. The first permit allows HTTP from the internal subnet to the web server, and the second permit allows ICMP echo-reply from any source. The implicit deny at the end blocks all other traffic.
Related concept
Static NAT maps one inside address to one outside address.
✗
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN out
Why it's wrong here
This is incorrect because the ACL is applied outbound instead of inbound on the internal-facing interface. The task specifically requires the ACL to be applied inbound on the interface facing the internal network.
✗
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in
Why it's wrong here
This is incorrect because the ICMP permit statement allows all ICMP types, not just echo-reply. The task specifically requires only ICMP echo-reply to be permitted.
✗
ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in
!
interface GigabitEthernet0/1
ip access-group BRANCH_IN in
Why it's wrong here
This is incorrect because the ACL is applied to two interfaces, including the external-facing interface (G0/1). The task only requires the ACL to be applied inbound on the internal-facing interface.
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.
✓ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN inCorrect answer▾
Why this is correct
This configuration correctly defines the extended ACL with the required permit statements and applies it inbound on the internal-facing interface. The first permit allows HTTP from the internal subnet to the web server, and the second permit allows ICMP echo-reply from any source. The implicit deny at the end blocks all other traffic.
✗ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN outWrong answer — click to see why▾
Why this is wrong here
The ACL is applied in the wrong direction. Applying it outbound would filter traffic leaving the interface, not entering it.
Why candidates choose this
Candidates might confuse the direction of traffic flow and think that outbound on the internal interface is correct because traffic from internal users goes out.
✗ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN inWrong answer — click to see why▾
Why this is wrong here
The ACL permits all ICMP traffic instead of only echo-reply. This violates the requirement to permit only ICMP echo-reply.
Why candidates choose this
Candidates may think that permitting all ICMP is acceptable or may forget to specify the echo-reply type, especially if they are used to allowing ping in both directions.
✗ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in
!
interface GigabitEthernet0/1
ip access-group BRANCH_IN inWrong answer — click to see why▾
Why this is wrong here
Applying the ACL to an additional interface (G0/1) is unnecessary and may cause unintended filtering. The requirement specifies only one interface.
Why candidates choose this
Candidates might think that applying the ACL to both interfaces provides better security, or they may misidentify which interface is internal.
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?”
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 200-301 NAT questions on configuration and troubleshooting.
Network Services and Security — This question tests Network Services and Security — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: ip access-list extended BRANCH_IN
permit tcp 192.168.1.0 0.0.0.255 host 203.0.113.10 eq 80
permit icmp any any echo-reply
!
interface GigabitEthernet0/0
ip access-group BRANCH_IN in — Option A is correct because it creates an extended ACL that permits TCP port 80 from the internal 192.168.1.0/24 to the web server 203.0.113.10 and permits only ICMP echo-reply, then applies it inbound on the internal interface G0/0, matching the requirement. Option B is wrong because the ACL is applied outbound on G0/0, but traffic from internal hosts to the web server exits via the WAN interface (G0/1), not G0/0. Option C is wrong because it permits all ICMP (any any) instead of only echo-reply, allowing unnecessary ICMP traffic. Option D is wrong because it applies the ACL inbound on both G0/0 and G0/1; applying it on G0/1 would incorrectly filter inbound traffic from the ISP, potentially blocking the web server's responses.
What should I do if I get this 200-301 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 200-301 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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