Sample Questions and Answers
Question 1
You are troubleshooting a network issue where users cannot access an internal web server. The server is accessible by IP but not by hostname. What is the most likely cause?
A. DNS misconfiguration
B. Web server port misconfiguration
C. ARP table corruption
D. Routing loop
Answer: A. DNS misconfiguration
Explanation: If the server is accessible by IP but not hostname, the issue is likely DNS-related. This means the hostname is not being resolved to an IP address.
Question 2
Which Cisco command helps verify whether the routing protocol OSPF is enabled on an interface?
A. show ip protocols
B. show ip ospf neighbor
C. show ip ospf interface
D. show ip interface brief
Answer: C. show ip ospf interface
Explanation: This command lists interfaces running OSPF, including area assignment and OSPF-specific details.
Question 3
While checking a Layer 3 switch, you notice one VLAN’s SVI is down/down. What is the most likely cause?
A. No device is connected to the VLAN
B. The VLAN has no IP address
C. The VLAN interface is administratively down
D. No active port is assigned to the VLAN
Answer: D. No active port is assigned to the VLAN
Explanation: SVIs require at least one up/up port in that VLAN to move to an up/up state.
Question 4
What does the %CDP-4-DUPLEX_MISMATCH log message indicate?
A. Interface speed mismatch
B. Subnet mismatch
C. CDP is disabled
D. One side is full-duplex and the other is half-duplex
Answer: D. One side is full-duplex and the other is half-duplex
Explanation: This message indicates a duplex mismatch between two connected devices, often causing performance issues.
Question 5
Which of the following is a potential cause of flapping OSPF neighbor adjacencies?
A. Interface MTU mismatch
B. Mismatched IP addresses
C. Incorrect route summarization
D. Access-list blocking OSPF packets
Answer: A. Interface MTU mismatch
Explanation: OSPF requires matched MTU settings for adjacency. Mismatches can cause frequent resets.
Question 6
You suspect a routing loop in your network. Which command can help you detect it?
A. show ip route
B. traceroute
C. show cdp neighbors
D. ping
Answer: B. traceroute
Explanation: Traceroute reveals the path a packet takes. If a routing loop exists, traceroute will show repeating hops.
Question 7
HSRP is configured but users complain of intermittent access. What might be wrong?
A. Incorrect standby IP configuration
B. Preemption not configured
C. Standby priority is equal
D. Physical interface is shut down
Answer: B. Preemption not configured
Explanation: Without preemption, a higher-priority router may not take over after recovery, leading to unexpected behavior.
Question 8
What command shows whether a router received a specific EIGRP route from a neighbor?
A. show ip route eigrp
B. show ip eigrp topology
C. show ip protocols
D. show ip eigrp neighbors
Answer: B. show ip eigrp topology
Explanation: This command displays the EIGRP topology database including feasible successors and routes received.
Question 9
You see %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to down. What is the likely cause?
A. Loopback interfaces never go down
B. Loopback has no IP address
C. Shutdown was issued
D. Misconfigured static route
Answer: C. Shutdown was issued
Explanation: Loopback interfaces are always up unless manually shut down.
Question 10
An engineer observes that traffic from a remote site is using the backup link instead of the primary. What is the most likely cause?
A. BGP administrative distance is too high
B. IP SLA not configured
C. Static route preference is lower than OSPF
D. EIGRP is preferred over BGP
Answer: B. IP SLA not configured
Explanation: IP SLA helps monitor the primary link and can dynamically change routes when the primary fails.
Question 11
You’re unable to form an EIGRP neighbor relationship. Which condition must be true?
A. Interfaces must be passive
B. Authentication must be enabled
C. The same autonomous system number must be used
D. Static routes must be present
Answer: C. The same autonomous system number must be used
Explanation: EIGRP routers must share the same AS number to become neighbors.
Question 12
Which command helps determine whether BGP routes are filtered?
A. show ip bgp summary
B. show ip route
C. show ip bgp neighbors
D. debug ip routing
Answer: C. show ip bgp neighbors
Explanation: This shows filters applied on inbound and outbound updates.
Question 13
A router receives a packet with TTL = 1. What will it do?
A. Forward the packet
B. Drop the packet and send ICMP Time Exceeded
C. Reset TTL to 255
D. Create a routing loop
Answer: B. Drop the packet and send ICMP Time Exceeded
Explanation: TTL=1 decrements to 0 on the next hop, triggering a drop.
Question 14
Which command checks if a DHCP binding was assigned to a specific host?
A. show ip dhcp pool
B. show ip dhcp binding
C. show running-config
D. show ip interface brief
Answer: B. show ip dhcp binding
Explanation: This lists IP-to-MAC address mappings.
Question 15
A switch interface is err-disabled. Which command helps determine the cause?
A. show interfaces status
B. show errdisable recovery
C. show interfaces
D. show port-security
Answer: B. show errdisable recovery
Explanation: Displays the reason for the err-disabled state and auto-recovery timers.
Question 16
Which of the following would not prevent OSPF adjacency?
A. Authentication mismatch
B. Hello/dead interval mismatch
C. Area ID mismatch
D. Static routing configuration
Answer: D. Static routing configuration
Explanation: Static routing doesn’t interfere with OSPF adjacency formation.
Question 17
You suspect asymmetric routing in your network. Which tool helps confirm this?
A. Ping
B. Debug ip routing
C. Traceroute
D. NetFlow
Answer: D. NetFlow
Explanation: NetFlow shows flow direction and allows for asymmetric path detection.
Question 18
A router redistributes static routes into OSPF but they aren’t seen in the topology. Why?
A. Static routes are not in the routing table
B. OSPF redistribution is disabled by default
C. Route-maps are required
D. Metric is missing
Answer: D. Metric is missing
Explanation: OSPF requires a metric when redistributing routes.
Question 19
Which condition triggers STP TCN (Topology Change Notification)?
A. Root bridge election
B. VLAN deletion
C. Port transitioning to forwarding
D. Link-layer protocol mismatch
Answer: C. Port transitioning to forwarding
Explanation: TCNs are generated when a port changes from blocking to forwarding.
Question 20
Which command verifies HSRP status?
A. show standby brief
B. show ip route
C. show spanning-tree
D. show ip protocols
Answer: A. show standby brief
Explanation: This shows HSRP group number, state, priority, and active/standby roles.
Question 21
What does a continuously incrementing input error count on an interface suggest?
A. Duplex mismatch
B. Interface shutdown
C. Normal operation
D. Congestion control
Answer: A. Duplex mismatch
Explanation: Collisions due to duplex mismatches cause input errors to rise.
Question 22
You see D EX in the routing table. What does it mean?
A. Default route
B. EIGRP external route
C. Dynamic static route
D. Default OSPF export
Answer: B. EIGRP external route
Explanation: D EX indicates an external EIGRP route redistributed into the AS.
Question 23
What’s the default HSRP priority?
A. 50
B. 100
C. 200
D. 255
Answer: B. 100
Explanation: Default HSRP priority is 100 unless manually set.
Question 24
Which command checks if IP SLA is active?
A. show ip sla monitor statistics
B. show ip sla statistics
C. show ip sla config
D. show monitor
Answer: B. show ip sla statistics
Explanation: Displays current SLA operation statistics and success rates.
Question 25
You’ve configured an extended ping, but receive no response. Which issue could be the cause?
A. Ping packet size
B. IP routing disabled
C. Source IP not reachable
D. OSPF neighbor down
Answer: C. Source IP not reachable
Explanation: If the source IP address used in extended ping isn’t reachable, replies won’t be received.
Question 26
How can you identify if a route is being filtered by distribute-list in EIGRP?
A. show ip eigrp neighbors
B. show ip protocols
C. debug eigrp fsm
D. show ip eigrp topology all-links
Answer: B. show ip protocols
Explanation: This command lists distribute-lists and other filtering mechanisms.
Question 27
In STP, a port in the blocking state:
A. Forwards user traffic
B. Listens for BPDUs
C. Transmits BPDUs
D. Learns MAC addresses
Answer: B. Listens for BPDUs
Explanation: Blocking ports only listen to BPDUs to prevent loops.
Question 28
Which logging level includes error messages about software issues?
A. 0 – Emergency
B. 2 – Critical
C. 3 – Errors
D. 5 – Notifications
Answer: C. 3 – Errors
Explanation: Level 3 logs errors that may affect functionality.
Question 29
What type of route is automatically created when a subnet is configured on an interface?
A. Static route
B. Connected route
C. Dynamic route
D. Null route
Answer: B. Connected route
Explanation: Connected routes are created automatically when IPs are configured on active interfaces.
Question 30
What is required to form a BGP peering?
A. Matching AS number
B. Directly connected peers
C. Reachable TCP port 179
D. Identical router IDs
Answer: C. Reachable TCP port 179
Explanation: BGP uses TCP port 179 to establish sessions between peers, even across different ASes.
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