CCNA Network Infrastructure and Connectivity Practice Test 8 — 15 Questions

Question 1

Which TWO statements are correct regarding Protocol Data Units (PDUs) and data encapsulation in the OSI model?

Accepted Answer

Data is encapsulated with a TCP header at the Transport layer to form a segment.. At the Transport layer, the TCP protocol adds a TCP header to the payload data, forming a segment. This encapsulation process is fundamental to reliable data delivery, as the TCP header includes source and destination ports, sequence numbers, and acknowledgment numbers for connection-oriented communication. At the Network layer, the IP protocol adds an IP header to the segment, forming a packet. The packet is the Network layer PDU, and the IP header contains logical addressing information such as source and destination IP addresses.

Answer

The PDU at the Transport layer is called a frame.

Answer

The Data Link layer adds a header and trailer to create a bit.

Answer

Encapsulation occurs as data moves up the OSI layers from Physical to Application.

Question 2

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 3

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 4

A network engineer notices that after issuing the no shutdown command on interface GigabitEthernet0/0 of a router, the interface remains down. The output of show interfaces GigabitEthernet0/0 displays 'GigabitEthernet0/0 is down, line protocol is down'. The physically connected switch port is also administratively down. What is the most likely cause?

Accepted Answer

The connected switch port is administratively down.. The output 'GigabitEthernet0/0 is down, line protocol is down' indicates that both Layer 1 and Layer 2 are down. Since the directly connected switch port is administratively down, the router interface detects no carrier and remains down/down even after the local no shutdown command. Therefore, option A is the most likely cause.

Answer

Mismatched encapsulation types on the router and switch.

Answer

Speed and duplex mismatch between the router and switch.

Answer

Incorrect native VLAN configuration on the trunk link.

Question 5

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 6

A branch router has two equal-cost static routes to the same destination network. Both routes are displayed in the output of the show ip route command, and pings from the router to both next-hop IP addresses succeed. Despite this, all traffic heading toward that destination is egressing only a single interface. The technician suspects Cisco Express Forwarding (CEF) is not performing load balancing as expected. What should the technician do next?

Accepted Answer

Issue the show ip cef detail command to inspect the CEF FIB entry and verify both adjacencies are present.. CEF performs load balancing over equal-cost paths using a hash of the packet's destination (or source/destination) address to select a path. The interface bandwidth is not a factor for equal-cost load balancing; it is used for metric calculation in routing protocols, not for CEF path selection. When traffic uses only one interface despite two equal-cost routes in the routing table, you should verify that CEF has installed both paths in its FIB and resolved both next-hop addresses to adjacencies. The command 'show ip cef detail' displays the FIB entry and associated adjacencies, confirming both paths are available for load balancing.

Answer

Check the interface output rates with show interface to see if both interfaces are transmitting traffic.

Answer

Display the routing table again with show ip route to ensure both static routes are still installed.

Answer

Verify the bandwidth configured on the outgoing interfaces using show interfaces or show running-config.

Question 7

An interface is configured with 10.24.7.158/27. What is the broadcast address of that subnet?

Accepted Answer

10.24.7.159. A /27 uses blocks of 32 addresses. The block containing .158 is 10.24.7.128 through 10.24.7.159, so .159 is the broadcast address.

Answer

10.24.7.191

Answer

10.24.7.127

Answer

10.24.7.160

Question 8

Which two statements accurately compare TCP and UDP? (Choose two.)

Accepted Answer

TCP provides connection-oriented transport. TCP is connection-oriented and uses sequencing, acknowledgments, and related controls. UDP is simpler and has lower overhead, but it does not guarantee delivery.

Answer

UDP guarantees delivery through acknowledgments

Answer

TCP does not use port numbers

Answer

UDP is always faster because it avoids congestion

Question 9

Which medium is the most common choice for a 10G uplink between wiring closets on different floors of the same building?

Accepted Answer

Fiber optic cable. Fiber is commonly used for building uplinks because it supports higher bandwidth and longer distances than typical copper for this use case.

Answer

Rollover cable

Answer

Coaxial cable

Answer

Console cable

Question 10

At which OSI layer do routers make forwarding decisions based on logical addressing?

Accepted Answer

Layer 3. Routers operate at the network layer when making forwarding decisions based on logical Layer 3 addresses such as IPv4 or IPv6 destination addresses.

Answer

Layer 1

Answer

Layer 2

Answer

Layer 4

Question 11

Which command enables IPv6 routing on a Cisco router?

Accepted Answer

ipv6 unicast-routing. The global configuration command 'ipv6 unicast-routing' enables IPv6 forwarding on a Cisco router. 'ipv6 enable' is an interface-level command used to enable IPv6 on a specific interface, not globally. 'ip routing ipv6' and 'ipv6 route enable' are syntactically invalid commands that do not exist in Cisco IOS.

Answer

ipv6 enable

Answer

ip routing ipv6

Answer

ipv6 route enable

Question 12

A host sends traffic to a web server on another subnet. Which address is used as the destination MAC address in the first Ethernet frame sent by the host?

Accepted Answer

The MAC address of the local default gateway. When a host wants to communicate with a device on a different subnet, it cannot reach that device directly. The host must send the frame to its default gateway, which is the router that connects to other subnets. Therefore, the destination MAC address in the first Ethernet frame is the MAC address of the local default gateway, not the remote web server (A). The DNS server (C) is used for name resolution, not for forwarding traffic. The broadcast MAC address (D) would send the frame to all devices on the local subnet, which is not appropriate for unicast communication to a remote destination.

Answer

The MAC address of the remote web server

Answer

The MAC address of the DNS server

Answer

The broadcast MAC address

Question 13

A branch office needs four subnets from the 192.168.50.0/24 network, with each subnet supporting up to 50 hosts. Which prefix length should be used for each subnet?

Accepted Answer

/26. Each subnet must support at least 50 hosts, so /26 is the smallest suitable prefix because it provides 62 usable addresses. A /24 can be split into exactly four /26 subnets.

Answer

/25

Answer

/27

Answer

/28

Question 14

A host sends an IPv4 packet larger than the outgoing interface MTU, and the DF bit is not set. What will a router normally do?

Accepted Answer

Fragment the packet before forwarding. If fragmentation is allowed, an IPv4 router can fragment a packet to fit the outgoing interface MTU. If DF were set, the router would instead drop the packet and typically send an ICMP message back to the source.

Answer

Drop the packet without notification

Answer

Convert the packet into UDP

Answer

Forward it unchanged and let the switch fragment it

Question 15

Which IPv6 address type is automatically created on an interface and used for communication on the local link only?

Accepted Answer

Link-local. Every IPv6-enabled interface generates a link-local address, typically in the FE80::/10 range. It is used for neighbor discovery, local communication, and next-hop resolution on the same link.

Answer

Global unicast

Answer

Unique local

Answer

Multicast