CCNA Practice Test 34 — 15 Questions

Question 1

A network engineer is configuring a new access switch that will connect to a distribution switch. The engineer must ensure that local hosts are placed in the correct VLANs before enabling trunking to the distribution switch to prevent VLAN mismatches and broadcast issues. Drag and drop the steps into the correct order.

Accepted Answer

Create VLANs → Assign access ports → Configure 802.1Q trunks with native VLAN → Verify with show vlan brief and show interfaces trunk. The correct order is to create VLANs first, then assign access ports to those VLANs so local hosts are properly placed and operational. Only then should 802.1Q trunks be configured to extend VLANs to other switches, because trunking before access port assignment could lead to operational inconsistencies. Options B and D would require access ports before VLANs exist, and Option C configures trunks prematurely in this scenario.

Question 2

Refer to the exhibit. A network administrator runs the show vlan brief command on SW2. Interface GigabitEthernet0/2 is intended to be an access port in VLAN 10, but it does not appear in the output. What is the most likely cause?

Accepted Answer

The interface is configured as a trunk port and therefore does not appear under any VLAN in show vlan brief.. The show vlan brief command lists only access ports that are statically or dynamically assigned to a VLAN. Trunk ports carry traffic for multiple VLANs and are not displayed in this table. The absence of GigabitEthernet0/2, despite VLAN 10 being active and containing other ports, indicates that the interface is likely operating as a trunk port.

Answer

The interface is configured with switchport mode dynamic auto and no trunk has been negotiated, causing it to be hidden.

Answer

The interface is administratively shut down, and down ports are excluded from the show vlan brief output.

Answer

VLAN 10 is not active, so the port assigned to it is not displayed in the listing.

Question 3

After configuring a trunk port to allow VLAN 40, a technician finds that VLAN 40 is not listed among the VLANs in spanning tree forwarding state in the show interfaces trunk output. What is the most likely cause?

Accepted Answer

VLAN 40 has not been created in the VLAN database on the switch.. Even if a VLAN is included in the trunk's allowed list, the switch cannot forward frames for that VLAN unless it exists in the local VLAN database. A non-existent VLAN is placed in a pruned state and will not appear as forwarding in show interfaces trunk. The allowed-list command worked, but the missing VLAN definition prevents the VLAN from being active on the trunk.

Answer

The trunk port is using ISL encapsulation, which does not support VLAN 40.

Answer

The technician omitted the 'add' keyword when adding VLAN 40 to the allowed list, so the trunk no longer permits VLAN 40.

Answer

VTP pruning is enabled, and VLAN 40 is not needed by any downstream neighbor, so it is pruned from this trunk.

Question 4

A technician is troubleshooting a network-wide broadcast storm that has caused severe performance issues. The technician notices that BPDU guard is globally enabled on the access layer switch, but no ports are in an err-disabled state. All access ports have PortFast enabled. What is the most likely cause?

Accepted Answer

BPDU filter is globally enabled, causing the switch to suppress BPDUs on PortFast ports and preventing BPDU guard from triggering.. When BPDU filter is enabled globally on a switch, it enables PortFast on all access ports and also prevents those ports from sending or receiving BPDUs. If a rogue switch is then connected to such a port, the switch does not detect any BPDU from it, so BPDU guard never triggers despite being enabled globally. This allows the rogue switch to create a bridging loop without STP intervention, leading to a broadcast storm.

Answer

Spanning tree is disabled globally, allowing the rogue switch to create a loop.

Answer

BPDU guard is misconfigured on the wrong ports, so it failed to block the rogue switch.

Answer

Root guard is incorrectly enabled on the access ports, causing the rogue switch to become the root bridge.

Question 5

Refer to the exhibit. A network engineer notices that on a four-link EtherChannel bundle between two switches, all traffic from a particular VLAN is being forwarded over only one physical link, while the other three links remain idle. The engineer suspects a load-balancing issue and issues the show etherchannel load-balance command, the output of which is shown. What is the most likely cause of the uneven traffic distribution?

Accepted Answer

The switch is using source‑MAC‑address load balancing, and multiple end hosts are appearing with the same source MAC address.. The exhibit shows the load-balancing method is 'src-mac'. When source-MAC-based hashing is used, all frames with the same source MAC address egress the same physical member link. If multiple end hosts are behind a router or proxy and appear with identical source MAC, the hash algorithm always selects the same link, leaving the other links in the bundle idle.

Answer

The EtherChannel is misconfigured with an LACP active/passive mode mismatch, forcing only one link to bundle.

Answer

VLAN pruning on the trunk has removed the VLAN from three of the four member interfaces.

Answer

Spanning Tree Protocol has blocked three of the four links in the EtherChannel because they form a loop.

Question 6

Users report that their PCs take over 30 seconds to obtain IP addresses and reach the network after being powered on. A network technician checks a switch port connected to a PC and observes that the port transitions through blocking, listening, learning, and then forwarding states, taking about 30 seconds to complete. The switch is running standard 802.1D STP. The technician confirms the port is an access port and only connects to a PC. What should the technician do next?

Accepted Answer

Enable PortFast on the access port.. The correct next action is to enable PortFast on the access port. PortFast allows a port to immediately transition to the forwarding state, bypassing the listening and learning phases, which is safe because the port connects only to an end device and cannot create a bridging loop. This directly resolves the 30-second boot-time delay without making network-wide changes.

Answer

Reduce the STP forward delay timer globally on the switch.

Answer

Disable STP on the access VLAN assigned to the port.

Answer

Enable Rapid PVST+ on the switch.

Question 7

A network engineer notices that a root port on a switch has transitioned to a loop-inconsistent state. The port was previously receiving BPDUs normally, but after a suspected unidirectional fiber cut, it no longer receives BPDUs. What is the most likely cause?

Accepted Answer

Loop Guard is active on the root port and transitioned it to loop-inconsistent state upon BPDU loss.. Loop Guard is an STP enhancement that monitors the reception of BPDUs on a blocked port. When BPDUs stop arriving (due to a unidirectional link failure), Loop Guard moves the port to loop-inconsistent state, preventing it from transitioning to the forwarding state and thus avoiding a switching loop.

Answer

BPDU Guard is enabled on the port, causing it to be placed in error-disabled state.

Answer

UDLD has detected a unidirectional link and has shut down the port.

Answer

Root Guard is preventing the port from transitioning to designated forwarding after losing BPDUs.

Question 8

Refer to the exhibit. A network administrator is troubleshooting a trunk link between SW1 and SW2. The trunk on interface GigabitEthernet0/0 on SW1 is not passing traffic, and all VLANs are isolated. The administrator issues the command 'show interfaces GigabitEthernet0/0 trunk' on SW1. What is the most likely cause of the issue?

Accepted Answer

The trunk encapsulation is set to ISL on SW1, but the peer switch only supports 802.1Q.. The 'show interfaces GigabitEthernet0/0 trunk' output explicitly displays encapsulation 'isl' and status 'not-trunking'. This indicates that the port is configured for ISL encapsulation, but the trunk is not operational. Since the peer switch only supports 802.1Q, the encapsulation mismatch prevents the trunk from forming, causing the traffic isolation.

Answer

The native VLAN is mismatched between SW1 and SW2.

Answer

The interface is configured as an access port instead of a trunk.

Answer

The interface is administratively shut down.

Question 9

A network technician is troubleshooting an inter-VLAN routing issue on a multilayer switch. Hosts on VLAN 10 can reach the SVI for VLAN 10 (10.0.10.1) but cannot reach hosts on VLAN 20. The technician has verified that 'ip routing' is enabled and that the 'show ip route' command displays directly connected routes for both VLANs. No static routes are configured. What should the technician do next?

Accepted Answer

Check the ARP table for entries on VLAN 20.. Because the switch has directly connected routes for both VLANs and routing is enabled, the Layer 3 forwarding logic is intact. The failure from VLAN 10 hosts to VLAN 20 hosts suggests that the switch cannot resolve the destination host's MAC address on VLAN 20, preventing Layer 2 frame encapsulation. Checking the ARP table with 'show ip arp' or similar will reveal whether the destination IPv4 address has a valid MAC entry on the correct VLAN interface. This targets Layer 2—the most likely remaining failure point after Layer 3 has been verified.

Answer

Issue the 'show ip routing' command again to confirm routing is enabled.

Answer

Configure a default route pointing to the next-hop gateway.

Answer

Verify the VLAN membership of the destination host on VLAN 20.

Question 10

Refer to the exhibit. A network engineer is troubleshooting an OSPF adjacency issue between R1 and R2. The output of the show ip ospf neighbor command on R1 shows the neighbor relationship with R2 stuck in the EXSTART/DROTHER state. What is the most likely cause?

Accepted Answer

MTU mismatch on the link between R1 and R2, causing DBD packets to be dropped.. The output specifically shows neighbor 10.0.0.2 in the EXSTART/DROTHER state. This state indicates that the Database Description (DBD) packet exchange phase has not completed. The most common cause for a neighbor to remain stuck in EXSTART is an MTU mismatch on the link, causing DBD packets (which are larger than the MTU) to be silently dropped.

Answer

OSPF network type mismatch between R1 and R2, preventing full adjacency.

Answer

Duplicate OSPF Router IDs on R1 and R2, causing DBD packet rejection.

Answer

OSPF authentication mismatch on the link, causing DBD packets to be rejected.

Question 11

Why is a default route often described as a route of last resort?

Accepted Answer

Because it is used only when no more specific route matches.. It is described that way because it is used only when no more specific route matches the destination. In practical terms, the router checks for connected, static, or dynamic routes that describe the destination more precisely. If it finds none, the default route becomes the fallback path.

This phrase captures the default route’s purpose exactly. It is not the fastest route or the most specific route. It is simply the catch-all route for otherwise unknown destinations.

Answer

Because it always has the lowest bandwidth.

Answer

Because it is more specific than any other route.

Answer

Because it can be learned only through OSPF.

Question 12

A technician is troubleshooting an OSPF adjacency problem: R1 and R2 are not forming a neighbor relationship. R1's OSPF configuration includes the command 'network 192.168.1.0 0.0.0.255 area 0'. R2's GigabitEthernet0/0 is configured with IP address 10.1.1.1/30 and is participating in OSPF area 0. The engineer verifies that physical connectivity is fine and OSPF is enabled on R2. What is the most likely cause?

Accepted Answer

R1's network statement does not include the subnet of the link connecting R1 and R2.. R1's network statement uses a wildcard mask of 0.0.0.255, which exactly matches interfaces with IP addresses in the 192.168.1.0/24 range. The link between R1 and R2 uses the 10.1.1.0/30 subnet, so R1's interface on that link will have an IP address that does not fall within the network command. Because OSPF only activates on interfaces whose primary IP is covered by a network statement, OSPF is not running on R1's connecting interface; no Hello packets are sent, and the adjacency cannot form. The other options describe possible causes but do not align with the given configuration: no explicit network type change is mentioned, duplicate router-IDs are not indicated, and no timer modification is described.

Answer

The OSPF network type on R1's interface differs from the network type on R2's interface.

Answer

R1's router ID is not manually set and duplicates the router ID of R2.

Answer

Mismatched OSPF hello and dead intervals between the routers.

Question 13

Refer to the exhibit. A network technician is troubleshooting router R1, which cannot reach hosts on the internet. R1 is connected to an ISP router at 203.0.113.1. The exhibit shows the output of the show ip route command. What is the most likely cause of the issue?

Accepted Answer

A static default route is not configured on R1, and OSPF is not advertising a default route.. The exhibit shows 'Gateway of last resort is not set' and no route entry for 0.0.0.0/0 (default route). Without a default route, R1 has no path to forward unknown destinations, such as internet hosts. The OSPF neighbor is active (192.168.2.0/24 learned via OSPF), but no default route is being originated by OSPF. Therefore, a static default route or OSPF default-information originate command is missing.

Answer

The OSPF neighbor relationship with the ISP router is down.

Answer

The interface connecting to the ISP router is in a shutdown state.

Answer

An incorrect next-hop address was specified in the static default route, making the route invalid.

Question 14

A network engineer notices that R1 is using the static route to 192.168.10.0/24 via next-hop 10.1.1.2 instead of the OSPF route via 10.2.2.2, even though the OSPF path has lower latency. What is the most likely cause?

Accepted Answer

The static route has a lower administrative distance than the OSPF route.. The static route is preferred because it has an administrative distance (AD) of 1, which is lower than OSPF's AD of 110. When multiple routes to the same destination exist from different routing sources, the route with the lowest AD is selected first. The static route's path might be slower, but AD comparison happens before any metric comparison. To use the OSPF path, the static route must be removed or given a higher AD.

Answer

The OSPF route has a higher metric than the static route.

Answer

Equal-cost multi-path (ECMP) is disabled for OSPF.

Answer

The static route is configured with a higher next-hop IP address, so it is preferred.

Question 15

Refer to the exhibit. A network administrator is troubleshooting an OSPF adjacency on R1's GigabitEthernet0/0 interface connected directly to R2. R2 is powered on and shows correct OSPF configuration, but the adjacency is stuck in the INIT or DOWN state. Based on the output, what is the most likely cause of the failure?

Accepted Answer

The OSPF passive-interface command has been applied to GigabitEthernet0/0, preventing hello packets from being sent.. The command output explicitly shows 'No Hellos (Passive interface)', confirming that the passive-interface command has been applied to GigabitEthernet0/0. With this configuration, OSPF does not send or receive hello packets on the interface, preventing any adjacency from forming with the directly connected neighbor R2.

Answer

The OSPF network type on R1's GigabitEthernet0/0 does not match the network type on R2.

Answer

The OSPF hello and dead timers on R1 do not match those configured on R2.

Answer

The GigabitEthernet0/0 interface on R1 has been assigned to a different OSPF area than R2's connected interface.