CCNA Switching and Network Access Practice Question
Exhibit
R1# show monitor capture CAP1 buffer brief # size timestamp source destination protocol 1 64 00:01:23.456 192.168.10.10 192.168.10.1 ICMP 2 64 00:01:23.789 192.168.10.10 192.168.10.1 ICMP 3 60 00:01:24.123 192.168.10.1 192.168.10.10 ARP 4 60 00:01:24.456 192.168.10.10 192.168.10.1 ICMP 5 60 00:01:24.789 192.168.10.1 192.168.10.10 ARP 6 60 00:01:25.123 192.168.10.10 192.168.10.1 ICMP R1# show ip interface vlan 10 Vlan10 is up, line protocol is up Internet address is 192.168.10.1/24 Broadcast address is 255.255.255.255 Address determined by non-volatile memory MTU is 1500 bytes Helper address is not set Directed broadcast forwarding is disabled Outgoing access list is not set Inbound access list is not set Proxy ARP is enabled Local Proxy ARP is disabled Security level is default Split horizon is enabled ICMP redirects are always sent ICMP unreachables are always sent ICMP mask replies are never sent IP fast switching is enabled IP CEF switching is enabled IP Null turbo vector IP multicast fast switching is enabled IP multicast distributed fast switching is disabled IP route-cache flags are Fast, CEF Router Discovery is disabled IP output packet accounting is disabled IP access violation accounting is disabled TCP/IP header compression is disabled RTP/IP header compression is disabled Policy routing is disabled Network address translation is disabled BGP Policy Mapping is disabled Input features: MCI Check Output features: None WCCP Redirect outbound is disabled WCCP Redirect inbound is disabled WCCP Redirect exclude is disabled
A network administrator is troubleshooting an issue where hosts on VLAN 10 cannot ping the default gateway at 192.168.10.1. The router (R1) has an SVI for VLAN 10 with IP 192.168.10.1/24. The administrator captures traffic on the router's G0/0/0 interface (trunk to the switch) and reviews the embedded packet capture output. What is the root cause of the problem?
⚠ Common exam trap
Cisco often tests the distinction between Layer 2 and Layer 3 issues, and the trap here is that candidates assume the problem is on the router (e.g., ACL or interface state) when the packet capture reveals that the traffic never reaches the router's SVI due to a VLAN mismatch on the switch access port.
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 switch port connecting the host is configured in the wrong VLAN (e.g., VLAN 20 instead of VLAN 10).
The captured traffic on the trunk shows that the router is not receiving any frames tagged with VLAN 10 from the host. If the switch port connecting the host is configured in VLAN 20 instead of VLAN 10, the host's frames will be tagged with VLAN 20 (or remain untagged in the access VLAN 20) and will not reach the router's SVI for VLAN 10, causing the ping to fail. This is the most direct cause given the symptom that the host cannot ping the default gateway.
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 router's SVI for VLAN 10 is administratively down.
Why it's wrong here
The 'show ip interface vlan 10' output reveals that VLAN 10's SVI is in an up/up state, meaning Layer 1 and Layer 2 are operational. An administratively down SVI would show 'administratively down' and the line protocol would be down, which would prevent the router from sending or receiving ARP frames on that VLAN. Since the router is actively sending ARP requests to resolve the host, the SVI cannot be administratively down.
- ✓
The switch port connecting the host is configured in the wrong VLAN (e.g., VLAN 20 instead of VLAN 10).
Why this is correct
The router is sending ARP requests, but the host never receives them because the switch port is in a different VLAN. This prevents the router from learning the host's MAC address, causing the ping to fail.
- ✗
An inbound ACL on the router's SVI is blocking ICMP echo requests from the host.
Why it's wrong here
The packet capture taken on the router's SVI shows ICMP echo requests from the host were received by the router, proving that no inbound ACL is denying them. An inbound ACL would be evaluated before the packet is processed by the router's forwarding engine, and a deny statement would cause the router to silently drop the packet without any response. Because the router continues processing the echo requests and attempts to reply, the hypothesis of an inbound ICMP ACL is contradicted.
- ✗
The router has ICMP redirects enabled, causing it to ignore the pings.
Why it's wrong here
ICMP redirects are a control mechanism used by a router to tell a host that a better next-hop exists for a particular destination; they do not suppress or ignore incoming ping packets. Even if redirects were enabled on the SVI, the router would still process the ICMP echo request and generate an echo reply. Moreover, the router is actively sending ARP replies, proving that it is forwarding frames normally, so an ICMP redirect configuration is not the cause of the ping failure.
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 switch port connecting the host is configured in the wrong VLAN (e.g., VLAN 20 instead of VLAN 10).Correct answer▾
Why this is correct
The router is sending ARP requests, but the host never receives them because the switch port is in a different VLAN. This prevents the router from learning the host's MAC address, causing the ping to fail.
✗The router's SVI for VLAN 10 is administratively down.Wrong answer — click to see why▾
Why this is wrong here
The SVI is operational, so this cannot be the root cause.
✗An inbound ACL on the router's SVI is blocking ICMP echo requests from the host.Wrong answer — click to see why▾
Why this is wrong here
The router receives the ICMP requests, so an inbound ACL would have dropped them before they reached the capture buffer.
✗The router has ICMP redirects enabled, causing it to ignore the pings.Wrong answer — click to see why▾
Why this is wrong here
ICMP redirects do not prevent the router from responding to pings; they only send redirect messages when appropriate.
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
Configuring Switch Ports for Desktops, VoIP Phones, APs, IoT, and Virtualized Hosts
Key term
ICMP
ICMP is a network-layer protocol used by network devices to send error messages and operational information about network connectivity.
Key term
Packet
A packet is a small unit of data that is sent over a network, containing both the actual data and control information for delivery.
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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.