CCNA Network Infrastructure and Connectivity Practice Test 8 — 15 Questions

Question 1

You are connected via the console to SW1, a Cisco Catalyst 2960 switch. The network administrator reports that users in VLAN 10 (Sales) cannot ping the default gateway 192.168.10.1, which is on R1's GigabitEthernet0/1 interface. SW1's interface GigabitEthernet0/1 connects to R1 and is configured as an access port in VLAN 10. R1's interface GigabitEthernet0/1 is configured with IP 192.168.10.1/24 and no shutdown. However, the link between them is up but the line protocol is down on both sides.

Accepted Answer

Configure the switchport to use the same speed and duplex settings as the router interface.. The symptom 'line protocol is down' while the physical link is 'up' on both sides indicates a Layer 1/2 mismatch, most commonly a speed/duplex negotiation failure. When a switch port and router interface are hardcoded to different duplex or speed settings (e.g., one side full-duplex, the other half-duplex or auto), the link may come up physically but the line protocol fails to initialize. Configuring matching speed and duplex settings resolves this mismatch and brings the line protocol up, allowing VLAN 10 traffic to flow.

Answer

Change the switchport mode to trunk to allow VLAN 10 traffic to pass to the router.

Answer

Assign the IP address 192.168.10.1 to the switch's VLAN 10 interface.

Answer

Enable CDP on both devices to verify neighbor information.

Question 2

You are connected via the console to R1, a Cisco ISR 4331 router. The network uses IPv6. R1's GigabitEthernet0/0 interface has the MAC address 00:1C:0F:9A:7B:32. You need to configure the interface to use EUI-64 to form a global unicast address from the prefix 2001:DB8:CAFE:1::/64. Additionally, ensure that the interface is enabled for IPv6.

Accepted Answer

R1(config-if)# ipv6 address 2001:DB8:CAFE:1::/64 eui-64
R1(config-if)# no shutdown. The correct command to configure an EUI-64 address is 'ipv6 address prefix/length eui-64'. The prefix must be specified with the :: abbreviation to leave the interface ID unspecified. Option B correctly uses the prefix 2001:DB8:CAFE:1::/64 and the eui-64 keyword, and includes 'no shutdown' to enable the interface. Option A incorrectly includes a full interface ID in the command, which is not allowed with the eui-64 keyword. Option C does not include the eui-64 keyword, so it configures a static address. Option D uses an incorrect interface ID (missing the bit inversion). Therefore, the correct answer is B.

Answer

R1(config-if)# ipv6 address 2001:DB8:CAFE:1:021C:0FFF:FE9A:7B32/64 eui-64
R1(config-if)# no shutdown

Answer

R1(config-if)# ipv6 address 2001:DB8:CAFE:1:021C:0FFF:FE9A:7B32/64
R1(config-if)# no shutdown

Answer

R1(config-if)# ipv6 address 2001:DB8:CAFE:1:001C:0FFF:FE9A:7B32/64 eui-64
R1(config-if)# no shutdown

Question 3

Which three options are valid steps for configuring a router-on-a-stick inter-VLAN routing setup? (Choose three.)

Accepted Answer

Create subinterfaces on the router for each VLAN.. In a router-on-a-stick configuration, the router uses subinterfaces to connect to multiple VLANs over a single physical interface. Each subinterface must be assigned an IP address that serves as the default gateway for its respective VLAN, and the router must have IP routing enabled (via the 'ip routing' command) to forward traffic between these subinterfaces. The three incorrect options fail because: configuring switch ports as access ports in a single VLAN would restrict connectivity to only that VLAN, breaking inter-VLAN routing; setting the native VLAN on the trunk to match the management VLAN is not required and is unrelated to router-on-a-stick functionality; and using 'switchport mode access' on the router-facing switch port would turn the link into a non-trunk access link, preventing multiple VLANs from reaching the router.

Answer

Configure the switch ports that connect to the router as access ports in a single VLAN.

Answer

Set the native VLAN on the trunk to match the management VLAN on the switch.

Answer

Use the 'switchport mode access' command on the router-facing switch port.

Question 4

Which three of the following are functions of the Dynamic Host Configuration Protocol (DHCP) in a network? (Choose three.)

Accepted Answer

Providing the default gateway and DNS server information to clients.. Option B is correct because DHCP leases IP addresses to clients for a configurable duration, using the lease time value in the DHCPOFFER/DHCPACK so addresses are reclaimed and reused. Option A is correct because DHCP options such as option 3 (router/default gateway) and option 6 (DNS servers) are delivered in the DHCPOFFER/DHCPACK, allowing clients to configure their default gateway and DNS resolver automatically. Option F is correct because DHCP dynamically allocates IP addresses from a defined scope/pool, assigning them to hosts automatically without manual configuration. Option C is not a DHCP function; domain name resolution is performed by DNS servers. Option D is not a DHCP function; user authentication before network access is handled by 802.1X/NAC/RADIUS. Option E is not a DHCP function; private-to-public IP translation is performed by NAT, typically on a router or firewall.

Answer

Resolving domain names to IP addresses for client devices.

Answer

Authenticating users before granting network access.

Answer

Translating private IP addresses to public IP addresses for internet access.

Question 5

Which three of the following correctly describe the behavior of EtherChannel? (Choose three.)

Accepted Answer

It aggregates multiple physical links into a single logical link.. EtherChannel aggregates multiple physical links into a single logical link, increasing bandwidth and providing redundancy. It uses a hash algorithm (based on source/destination MAC, IP, or TCP/UDP ports) to distribute traffic across member links. All member ports must have identical speed and duplex settings and be on the same switch (or stack). The statement that EtherChannel allows multiple VLANs only if configured as an access port is false because EtherChannel links can operate as trunks to carry multiple VLANs.

Answer

It requires that member ports be on different switches to form a single channel.

Answer

It increases the total number of STP instances in the network.

Answer

It allows multiple VLANs on the same link only if configured as an access port.

Question 6

Which three of the following are required to implement inter-VLAN routing on a Cisco switch using a router-on-a-stick configuration? (Choose three.)

Accepted Answer

A trunk link between the switch and the router, carrying multiple VLANs.. In a router-on-a-stick configuration, inter-VLAN routing is achieved by connecting a single router to a switch via a trunk link. The trunk carries multiple VLANs (using 802.1Q tagging), and the router uses subinterfaces—each configured with an IP address in the respective VLAN subnet—to route traffic between VLANs. The switch port connecting to the router must be configured as a trunk (e.g., with the `switchport mode trunk` command) to allow all VLAN traffic to reach the router.

Answer

A separate physical router interface for each VLAN.

Answer

IP routing enabled on the switch.

Answer

A Layer 3 switch with routed ports.

Question 7

Which four of the following correctly describe characteristics or best practices for VLAN trunking and Layer 2 switch configuration? (Choose four.)

Accepted Answer

When connecting two switches, it is recommended to manually set the trunk mode to avoid DTP negotiation errors and security risks.. 802.1Q trunking defines a native VLAN that carries untagged traffic; both ends must agree on the native VLAN to prevent misdirection and security issues. DTP can negotiate trunking between Cisco switches when ports are set to dynamic desirable or trunk mode, allowing automatic trunk establishment. VTP in transparent mode forwards VTP advertisements to other switches but does not synchronize its VLAN database, making it safe for maintaining local VLAN control. Manually setting trunk mode is a best practice to avoid DTP negotiation errors and security risks, as DTP can be exploited. Option 1 is incorrect because using VLAN 1 for user traffic is a security vulnerability; it is recommended to change the native VLAN and prune VLAN 1. Option 3 is incorrect because an access port belongs to only one VLAN; VLAN pruning is used on trunk links to restrict VLAN traffic, not to allow an access port to carry multiple VLANs.

Answer

VLAN 1 is the default native VLAN on Cisco switches and is considered a best practice to use for all user traffic to simplify management.

Answer

A switchport configured as an access port can belong to multiple VLANs simultaneously if using VLAN pruning.

Question 8

Drag and drop the following steps into the correct order to troubleshoot a fiber optic link that is down on a Cisco switch using SFP transceiver diagnostics and interface commands.

Accepted Answer

Physically verify the fiber cable connectors are clean, undamaged, and correctly mated with the SFP transceiver.. First verify the fiber cable and connectors, then confirm the SFP is compatible and fully inserted. Use 'show interface' to check status and basic errors. Use 'show interfaces transceiver' to inspect optical transmit/receive power; this is meaningful even when the link is down (e.g., low receive power), as long as the SFP is recognized and supports DOM. Finally, examine error counters for CRC, runts, and giants.

Question 9

A network administrator captures traffic on Server B and finds that ICMP echo requests from Host A arrive, and the server generates corresponding echo replies, but these replies never appear on the wire. The server's routing table has a valid default gateway, and no ACLs are blocking the traffic. What is the most likely cause?

Accepted Answer

The switch port connecting Server B has port security enabled and has learned a different MAC.. The ICMP echo requests arrive at Server B, and the server generates replies, but they never appear on the wire. This indicates the server's frames are being dropped before reaching the network. Since the server has a valid default gateway and no ACLs are blocking, the most likely cause is that the switch port connecting Server B has port security enabled, and the allowed MAC address does not match the server's MAC. As a result, the switch drops the server's frames on ingress, preventing the replies from ever appearing on the wire. An incorrect ARP cache entry would still result in frames being transmitted on the wire, just with a wrong destination MAC, so it would not explain the complete absence of the replies.

Answer

The server's TCP stack is corrupt.

Answer

The server's ARP cache contains an incorrect MAC address for the destination host.

Answer

The server's routing table is missing a route to the source network.

Question 10

A network engineer notices that a workstation in VLAN 10 cannot communicate with hosts in VLAN 20. The workstation is connected to an access layer switch port that shows 'up/up' in show ip interface brief. The switch's trunk port to the router is up, and the router's sub-interface for VLAN 10 is also in an up/up state. The router-on-a-stick configuration appears operational, but inter-VLAN traffic still fails. What is the most likely cause?

Accepted Answer

The router sub-interface for VLAN 10 is missing the encapsulation dot1q command.. In a router-on-a-stick configuration, each sub-interface must use the `encapsulation dot1q <vlan-id>` command to process VLAN-tagged frames. Without this command, the sub-interface remains up/up but cannot route traffic for VLAN 10, preventing communication with VLAN 20. The up/up state does not guarantee proper frame tagging.

Answer

The switch port to the workstation is incorrectly configured as a trunk instead of an access port.

Answer

The native VLAN on the trunk between the switch and router is mismatched.

Answer

VLAN 10 is not allowed on the trunk link.

Question 11

Refer to the exhibit. An engineer is troubleshooting a connectivity issue where packets from the local network destined to host 192.168.1.200 are being dropped. The host 192.168.1.200 is configured with IP address 192.168.1.200/25, while the router’s GigabitEthernet0/0 interface is on the same physical segment. Based on the output, what is the most likely cause of the problem?

Accepted Answer

The router interface Gi0/0 is using a /24 subnet mask while the host is in a /25 subnet, so the host considers the router's IP address to be outside its own subnet and cannot reach its default gateway.. Router Gi0/0 has a /24 mask, so it considers 192.168.1.0/24 directly connected and will ARP for any address in that range, including 192.168.1.200. The host with /25 mask will still answer an ARP request for its own IP. The real problem is that the host's /25 subnet is 192.168.1.128/25, so the router's interface address (e.g., 192.168.1.1) is outside the host's subnet. This makes the default gateway unreachable from the host, so the host cannot send return traffic or any traffic outside its /25 subnet, breaking connectivity. The subnet mask mismatch is the root cause; the default gateway setting is not inherently incorrect.

Answer

The host 192.168.1.200 has an incorrect default gateway set, preventing it from communicating with the router.

Answer

An inbound access list on GigabitEthernet0/0 is blocking ICMP traffic from host 192.168.1.200.

Answer

The GigabitEthernet0/0 interface is in a shutdown state, preventing traffic from being forwarded to the host.

Question 12

Refer to the exhibit. A network engineer is troubleshooting an OSPFv2 neighbor adjacency that remains in the DOWN state between R1 and R2. The engineer issues the show cdp neighbors detail command on R1 and confirms that R1's GigabitEthernet0/1 interface is configured with IP address 192.168.1.1/30. What is the most likely cause of the problem?

Accepted Answer

The IP addresses on the connected interfaces are in different subnets.. OSPFv2 requires that neighboring interfaces share a common subnet to form an adjacency. The show cdp neighbors detail output confirms R1's GigabitEthernet0/1 is configured with IP address 192.168.1.1/30, but if R2's interface is on a different subnet (e.g., 192.168.2.0/30), the routers will not be able to communicate OSPF Hello packets, leaving the neighbor state in DOWN. This is a fundamental OSPF neighbor formation requirement, and a subnet mismatch will prevent the adjacency from progressing past the DOWN state.

Answer

The OSPF area IDs configured on R1 and R2 do not match.

Answer

There is an MTU mismatch between the two routers.

Answer

OSPF authentication is configured incorrectly on one of the routers.

Question 13

You are configuring a new Layer 2 switch (SW1) in a small office. The switch has a single management VLAN (VLAN 1) and is connected to router R1 via a trunk link. You need to assign an IP address to the switch's management interface so that you can manage it remotely. Which command sequence correctly assigns an IPv4 address to the management interface on a Cisco Catalyst switch?

Accepted Answer

SW1(config)# interface vlan 1
SW1(config-if)# ip address 192.168.1.10 255.255.255.0
SW1(config-if)# no shutdown. To manage a Cisco Catalyst switch remotely, you must assign an IP address to a Switch Virtual Interface (SVI) for the management VLAN. The correct procedure involves entering interface configuration mode for the SVI, assigning the IP address and subnet mask, and ensuring the interface is enabled with 'no shutdown'. Configuring a default gateway is also recommended for management from other subnets, but the core step is the SVI IP assignment and activation.

Answer

SW1(config)# interface vlan 1
SW1(config-if)# ip address 192.168.1.10 255.255.255.0
SW1(config-if)# exit
SW1(config)# ip default-gateway 192.168.1.1

Answer

SW1(config)# interface fastEthernet 0/1
SW1(config-if)# ip address 192.168.1.10 255.255.255.0
SW1(config-if)# no shutdown

Answer

SW1(config)# interface vlan 1
SW1(config-if)# ip address 192.168.1.10 255.255.255.0
SW1(config-if)# shutdown

Question 14

A network engineer is configuring a Cisco router (R1) to provide DHCP services to a LAN segment. The LAN uses the subnet 192.168.10.0/24, and the router's interface GigabitEthernet0/0 is configured with IP address 192.168.10.1/24. The engineer wants to exclude the first 10 IP addresses (192.168.10.1 through 192.168.10.10) from the DHCP pool because they are reserved for static assignments. Which configuration snippet correctly accomplishes this?

Accepted Answer

R1(config)# ip dhcp excluded-address 192.168.10.1 192.168.10.10
R1(config)# ip dhcp pool LAN
R1(dhcp-config)# network 192.168.10.0 255.255.255.0
R1(dhcp-config)# default-router 192.168.10.1. The correct configuration uses the global command 'ip dhcp excluded-address' to reserve a range of IP addresses from being assigned by DHCP, then defines the DHCP pool with the network, subnet mask, and default gateway. The exclusion command must be entered in global configuration mode. This ensures that the specified addresses are not offered to DHCP clients, allowing them to be used for static assignments.

Answer

R1(config)# ip dhcp excluded-address 192.168.10.1 192.168.10.10
R1(config)# ip dhcp pool LAN
R1(dhcp-config)# network 192.168.10.0 255.255.255.0
R1(dhcp-config)# default-router 192.168.10.1
R1(dhcp-config)# dns-server 8.8.8.8

Answer

R1(config)# ip dhcp excluded-address 192.168.10.1 192.168.10.10
R1(config)# ip dhcp pool LAN
R1(dhcp-config)# network 192.168.10.0 255.255.255.0
R1(dhcp-config)# default-router 192.168.10.1
R1(dhcp-config)# lease 0 8

Answer

R1(config)# ip dhcp pool LAN
R1(dhcp-config)# network 192.168.10.0 255.255.255.0
R1(dhcp-config)# default-router 192.168.10.1
R1(dhcp-config)# excluded-address 192.168.10.1 192.168.10.10

Question 15

A network engineer is configuring a new Cisco switch port that will connect to an IP phone. The phone must receive voice traffic in VLAN 20 and data traffic from a connected PC in VLAN 30. The engineer wants the phone to tag its own voice traffic and pass untagged data traffic from the PC. Which configuration should be applied to the switch port?

Accepted Answer

Configure the port as an access port in VLAN 30 and enable voice VLAN 20 with the switchport voice vlan 20 command.. The correct configuration uses an access port for the PC's untagged data traffic and a voice VLAN for the phone's tagged voice traffic. This allows a single switch port to support both an IP phone and a PC while maintaining separate VLANs for voice and data, which is a common Cisco design for unified communications.

Answer

Configure the port as an access port in VLAN 20 and enable voice VLAN 30 with the switchport voice vlan 30 command.

Answer

Configure the port as a trunk port with native VLAN 20 and allowed VLANs 20 and 30.

Answer

Configure the port as a dynamic auto port so it can negotiate both access and trunk modes with the phone.