CCNA Practice Test 33 — 15 Questions

Question 1

R1 and R2 are directly connected and running OSPF. The IP addressing is correct and both routers are in area 0, but they do not form an adjacency. What is the most likely cause?

Accepted Answer

The OSPF MTU values do not match on the connected interfaces.. The most likely cause is an MTU mismatch between the two interfaces. During the OSPF database exchange process, neighbors must agree on the MTU value to successfully exchange DBD packets; a mismatch typically causes the adjacency to become stuck in the ExStart or Exchange state. Basic connectivity (e.g., ping) often still works because ICMP packets are small, but the OSPF adjacency fails due to the MTU discrepancy.

Answer

The routers must use identical hostnames before OSPF can form neighbors.

Answer

The routers must use VLAN 1 for OSPF to operate.

Answer

The interfaces need to be configured as trunks instead of routed ports.

Question 2

A switch receives BPDUs on a user-facing port configured as an edge port, but instead of just blocking the port role it fully error-disables it. Which protection feature most likely explains that behavior?

Accepted Answer

BPDU Guard. BPDU Guard most likely explains that behavior. In practical terms, BPDU Guard is used to protect ports that are expected to face ordinary endpoints, not other switches. If BPDUs appear on such a port, the device treats that as a serious topology-policy violation and shuts the port down.

This is different from features that merely influence spanning-tree role choice without fully error-disabling the interface.

Answer

Root guard

Answer

Port security

Answer

DHCP snooping

Question 3

A switch is configured with DHCP snooping and Dynamic ARP Inspection. Hosts suddenly lose connectivity after changing IP settings manually. Which explanation is strongest?

Accepted Answer

DAI is rejecting ARP traffic because the manual IP change does not match trusted snooping bindings.. DAI uses DHCP snooping binding to validate ARP messages; a manual IP change creates a mismatch, causing DAI to block ARP. Option B is incorrect because STP prevents loops and does not block based on MAC address changes. Option C is incorrect because OSPF authentication is a routing protocol feature irrelevant on an access port. Option D is incorrect because PPP authentication applies to serial links, not Ethernet ARP.

Answer

STP is blocking the host because its MAC address changed.

Answer

OSPF authentication failed on the access port.

Answer

The switch requires PPP authentication before allowing ARP traffic.

Question 4

A network engineer notices that the system clock on a Cisco IOS-XE router is incorrect, causing syslog timestamps to be unreliable. The router is configured as an NTP client to synchronize with a remote NTP server at 192.168.1.10. However, the show ntp status command indicates the clock is unsynchronized. What is the most likely cause of this issue?

Accepted Answer

The router cannot reach the NTP server due to a missing route or firewall blocking UDP port 123.. NTP operates over UDP port 123. If the router cannot reach the NTP server at 192.168.1.10 due to a missing route or a firewall blocking UDP 123, the NTP client will remain unsynchronized, as indicated by the 'show ntp status' command showing the clock as unsynchronized. This is the most common cause of NTP synchronization failure in a network.

Answer

The NTP server is using TCP instead of UDP for NTP communication.

Answer

The NTP server has a higher stratum level than the router's local clock, so the router ignores it.

Answer

NTP authentication is misconfigured on the router.

Question 5

A network administrator wants to receive an immediate notification from a device when a significant event occurs, rather than polling the device repeatedly. Which SNMP feature is most associated with that requirement?

Accepted Answer

SNMP traps. SNMP traps are the correct answer because they are an SNMP feature that sends unsolicited, event-driven notifications from the device to the management system when a significant event occurs, eliminating the need for polling. Option B (syslog severity 7) is incorrect because syslog is a separate protocol for logging; while syslog messages are also sent unsolicited, the question specifically asks for an SNMP feature. Options C (DHCP relay) and D (NetFlow exporters) are unrelated to immediate event notifications: DHCP relay forwards broadcast requests, and NetFlow exports traffic flow data for analysis.

Answer

Syslog severity 7

Answer

DHCP relay

Answer

NetFlow exporters

Question 6

A company wants to connect two sites across an IP network by creating a logical tunnel between the edge routers. Which technology is most directly associated with that requirement?

Accepted Answer

GRE. GRE is the most directly associated technology because it creates a logical tunnel between routers across an existing IP network. In practical terms, it allows the routers to treat the path as a virtual point-to-point connection for encapsulated traffic.

The question is specifically about tunneling between sites, not about plain routing, management, or switching behavior.

Answer

PortFast

Answer

DHCP relay

Answer

Root guard

Question 7

A subnet uses the mask 255.255.255.224. How many usable host addresses does it provide?

Accepted Answer

30. A mask of 255.255.255.224 corresponds to a /27 prefix. In plain language, that leaves 5 host bits available in the address, which creates 32 total addresses in each subnet. Two of those are reserved: one for the network address and one for the broadcast address. That leaves 30 usable host addresses.

This is a classic subnetting question because it tests whether you can move from mask to prefix idea to host count without getting lost. Many learners remember the block size but forget to subtract the network and broadcast entries. The correct answer comes from that full logic chain: /27 means 32 total, and therefore 30 usable.

Answer

14

Answer

62

Answer

126

Question 8

A network engineer notices that the router interface GigabitEthernet0/1 is in an 'administratively down' state in the output of the show ip interface brief command, preventing connectivity to the subnet connected to that interface. What is the most likely cause?

Accepted Answer

The shutdown command is configured on the interface.. The 'administratively down' state in the output of 'show ip interface brief' indicates that the interface has been manually disabled using the 'shutdown' command. This is a Layer 1/2 administrative state, not a protocol or connectivity issue. To bring the interface up, the 'no shutdown' command must be applied in interface configuration mode.

Answer

The interface does not have an IP address assigned.

Answer

The interface is configured with an incorrect subnet mask.

Answer

An access list is blocking traffic on the interface.

Question 9

A router learns 192.168.30.0/24 from OSPF and also has a static route to 192.168.30.0/24 with administrative distance 200. Which route is installed in the routing table while both are available?

Accepted Answer

The OSPF route. The OSPF route is installed because its default administrative distance of 110 is lower than the static route’s configured administrative distance of 200. In practical terms, the static route has been intentionally made a backup. It is present in the configuration, but it does not become active while the lower-distance OSPF route is healthy.

This is a classic floating-static design question. The important point is that route-source preference depends on administrative distance when the prefix length is the same.

Answer

The static route

Answer

Both routes equally for load balancing

Answer

Neither route, because they conflict

Question 10

A host uses the subnet mask 255.255.255.240. How many usable host addresses exist in each subnet?

Accepted Answer

14. The mask 255.255.255.240 corresponds to /28. In practical terms, that leaves 4 host bits, which gives 16 total addresses in each subnet. After subtracting the network and broadcast addresses, 14 usable hosts remain.

This is a classic host-capacity calculation and a very common subnetting pattern on the exam.

Answer

12

Answer

16

Answer

30

Question 11

Which IPv6 prefix is used for link-local addresses?

Accepted Answer

FE80::/10. IPv6 link-local addresses come from FE80::/10. They are valid only on the local link and are commonly used for neighbor discovery and routing adjacency formation.

Answer

FC00::/7

Answer

2000::/3

Answer

FF00::/8

Question 12

Which two statements accurately describe a default gateway from a host perspective?

Accepted Answer

It is the next-hop path a host uses for destinations outside the local subnet.. A default gateway is the local router or Layer 3 interface that a host uses for traffic destined beyond its own subnet. In plain language, the host uses the gateway when the destination is not local. The default gateway does not replace the host’s own IP address or subnet mask; it complements them by providing the next-hop path for remote communication.

This is a foundational host-networking concept because many connectivity issues come from misunderstanding what the gateway actually does. The two correct answers are the ones that describe remote-traffic forwarding and the local next-hop role of the gateway.

Answer

It replaces the need for a subnet mask.

Answer

It is the same thing as a DNS server.

Answer

It is used only for ARP broadcasts.

Question 13

A network engineer configures OSPF between R1 and R2, but the routers never become neighbors on GigabitEthernet0/0. Based on the exhibit, what is the most likely cause?

Accepted Answer

The OSPF interface timers do not match.. The most likely cause is a hello/dead timer mismatch. In practical terms, both routers are on the same subnet and both are trying to run OSPF in area 0, so the obvious items look correct. But OSPF does not form adjacency based on IP reachability alone. It also checks whether key interface parameters agree. Hello and dead intervals are among those required parameters.

On R1, the hello interval is 10 seconds and the dead interval is 40 seconds. On R2, the hello interval is 5 seconds and the dead interval is 20 seconds. That mismatch is enough to prevent the neighbor relationship from forming. This is a common CCNA troubleshooting pattern because the interfaces can still ping each other, which makes the failure look less obvious at first glance.

Answer

The routers are using different OSPF areas.

Answer

The routers must use the same hostname to become neighbors.

Answer

The subnet mask prevents multicast OSPF traffic.

Question 14

Which two statements accurately describe subnet masks in IPv4?

Accepted Answer

It identifies the network-versus-host split in an IPv4 address.. A subnet mask tells the host which part of the IPv4 address refers to the network and which part refers to the host. In plain language, it helps the device determine whether a destination is local or remote. That decision is essential because it affects whether the host uses ARP directly or forwards traffic to the default gateway.

The wrong answers usually attribute unrelated behaviors to the subnet mask, such as encryption or hostname resolution. The two correct answers are the ones that preserve its role in defining local scope and address structure.

Answer

It resolves hostnames into IP addresses.

Answer

It encrypts packets before they leave the host.

Answer

It replaces the need for a default gateway.

Question 15

A router interface is configured with the prefix 2001:db8:acad:12::/64 and uses EUI-64 to build the interface ID. What is the main purpose of EUI-64 in this context?

Accepted Answer

It automatically creates the interface ID portion of the IPv6 address from the MAC address.. EUI-64 is used to automatically generate the interface identifier portion of the IPv6 address from the underlying MAC address. In practical terms, the /64 prefix provides the network portion, and EUI-64 helps derive the lower 64 bits without the administrator manually typing a full host portion. This can make addressing easier in environments where automatic formation is desired.

The important idea is that EUI-64 affects the interface ID, not the prefix length or the routing behavior of the network. It is an address-construction method, not a routing protocol.

Answer

It changes the /64 prefix into a /48 prefix for summarization.

Answer

It replaces the need for a link-local address.

Answer

It encrypts IPv6 traffic between neighbors.