How many OSPF Troubleshooting Scenarios questions are on this page?

This page has 14 OSPF Troubleshooting Scenarios scenario questions for the 350-601 exam, each with detailed explanations and wrong-answer analysis.

How should I approach 350-601 scenario questions?

Read the full scenario before looking at the answer options. Identify the constraint or requirement in the scenario, then eliminate options that are generally true but wrong for this specific case. Scenario questions reward careful reading over pattern matching.

← Back to Cisco DCCOR / CCNP Data Center Core 350-601 questions

Scenario-based practice

OSPF Troubleshooting Scenarios

Practise 350-601 Cisco DCCOR / CCNP Data Center Core 350-601 OSPF questions covering neighbour states, router IDs, areas, timers, passive interfaces, OSPF cost, route selection, and command-output troubleshooting.

Start full practice test Read exam guide

scenario questions

350-601

exam code

Cisco

vendor

Scenario guide

How to approach ospf troubleshooting scenarios

OSPF neighbour adjacencies, route advertisements, and DR/BDR elections appear consistently on the CCNA. These questions test whether you can read OSPF state from show commands and identify why two routers fail to reach FULL adjacency or why a route isn't being learned.

Quick answer

OSPF questions usually test neighbour formation, areas, router IDs, route preference, metrics and command-output interpretation.

How OSPF neighbours form and why adjacency can fail.

How router ID, area ID, timers, passive interfaces and authentication affect OSPF.

How OSPF cost influences route selection.

How to read show ip route and show ip ospf neighbor output.

Practice scenarios

Question 1mediumdrag order

Review the full OSPF breakdown →

Sequence the steps for configuring OSPF on a Cisco Nexus switch in a data center fabric.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 2easymultiple choice

Review the full OSPF breakdown →

A network engineer is configuring OSPF on a Cisco Nexus switch for a data center network. The requirement is to ensure that the switch does not become the Designated Router (DR) on a multi-access segment. Which OSPF configuration achieves this?

A
Set OSPF priority to 255 on the interface
Why wrong: Priority 255 increases the chance of becoming DR.
B
Set OSPF priority to 0 on the interface
Priority 0 means the router will never become DR or BDR.
C
Change the OSPF network type to point-to-point
Why wrong: Point-to-point network type eliminates DR election, but it changes the behavior for all routers; the question asks specifically to prevent this switch from becoming DR.
D
Configure the interface as passive under OSPF
Why wrong: Passive interface suppresses OSPF hellos, so no adjacency is formed; it does not prevent DR election if hellos are sent.

Full breakdown with real-world context →

Question 3mediummultiple choice

Review the full OSPF breakdown →

A network engineer is troubleshooting an OSPF adjacency issue between two Nexus switches. The neighbors are stuck in the EXSTART state. What is the most likely cause?

A
Hold timer mismatch
Why wrong: Hold timer mismatch causes adjacency to go down, not stuck in EXSTART.
B
Incorrect area ID
Why wrong: Area ID mismatch prevents neighbor discovery, not EXSTART.
C
MTU mismatch
MTU mismatch leads to DBD packet rejection, keeping the neighbor in EXSTART.
D
Duplicate router ID
Why wrong: Duplicate router IDs prevent adjacency formation entirely, not just EXSTART.

Full breakdown with real-world context →

Question 4hardmultiple choice

Review the full OSPF breakdown →

A large enterprise uses Cisco Nexus 9000 switches in a VXLAN EVPN fabric. The underlay is OSPF. Each leaf switch has a loopback0 interface as the source interface for VXLAN tunnel endpoints. After a maintenance window, an engineer modifies the IP address of loopback0 on leaf-5 from 10.1.1.5/32 to 10.1.1.105/32. Subsequently, all VXLAN tunnels to leaf-5 go down. OSPF adjacencies between leaf-5 and the spines are still FULL. The engineer checks the NVE interface on leaf-5 and sees the source-interface is loopback0 but the interface status is up/up. However, pings from other leaves to 10.1.1.105 fail. What is the most likely cause?

A
The OSPF process on leaf-5 was not restarted after the IP change
Why wrong: OSPF dynamically adjusts to IP changes; restart is not required.
B
The new loopback IP 10.1.1.105 is not included in the OSPF network statement under router ospf
The new IP subnet must be advertised via OSPF to be reachable by other leaves.
C
The MTU on loopback0 is set too low causing OSPF hello drops
Why wrong: OSPF adjacencies are still FULL, so MTU is not an issue.
D
The VXLAN source-interface was automatically changed to a different loopback
Why wrong: The source-interface remains configured as loopback0; it does not change automatically.

Full breakdown with real-world context →

Question 5easymultiple choice

Review the full OSPF breakdown →

A network engineer is configuring OSPF on a pair of Nexus 9000 switches acting as spine switches in a VXLAN fabric. The engineer needs to ensure that the spine switches do not become the DR for any VLAN. Which configuration should be applied?

A
Configure passive-interface default under OSPF.
Why wrong: Passive interface suppresses OSPF adjacencies, not DR election.
B
Set ospf network type to point-to-multipoint.
Why wrong: Point-to-multipoint still elects DRs in some scenarios.
C
Set ospf priority to 0 on the spine interfaces.
OSPF priority 0 prevents the router from participating in DR/BDR election.
D
Set ospf priority to 255 on the spine interfaces.
Why wrong: Priority 255 increases the chance of becoming DR.

Full breakdown with real-world context →

Question 6mediummultiple choice

Review the full OSPF breakdown →

During a network upgrade, an engineer applies a new OSPF configuration on a Nexus 9000 spine. After the change, several leaf switches lose connectivity to each other. The engineer examines the logs and sees OSPF adjacency flapping. What is the most likely cause?

A
Duplicate router IDs.
Duplicate router IDs cause OSPF neighbors to flap.
B
OSPF hello timer mismatch.
Why wrong: Hello timer mismatch would prevent adjacency from forming.
C
MTU mismatch on the fabric links.
Why wrong: MTU mismatch can cause problems but not typically flapping.
D
Incorrect area configuration.
Why wrong: Incorrect area would prevent adjacency entirely.

Full breakdown with real-world context →

Question 7mediummultiple choice

Review the full OSPF breakdown →

Refer to the exhibit. An engineer configured a VXLAN tunnel endpoint (VTEP) but the VXLAN tunnel is not operational. The underlay OSPF adjacency is established. What is the missing configuration?

Exhibit

interface nve1
 source-interface loopback0
 member vni 10000 mcast-group 239.1.1.1
!
interface loopback0
 ip address 10.10.10.1 255.255.255.255
!
interface Ethernet1/1
 no switchport
 ip address 192.168.1.1 255.255.255.0
 ip router ospf 1 area 0

A
The NVE interface must be enabled with the no shutdown command.
Why wrong: NVE interfaces are usually administratively up by default; no shutdown is not typically required.
B
The multicast group must be reachable via the underlay.
Why wrong: Multicast reachability affects BUM traffic but not the tunnel's operational status.
C
The loopback0 interface is not included in the OSPF process.
The loopback0 interface, used as the NVE source, is not advertised via OSPF, so its IP is unreachable from other VTEPs.
D
The VNI must be mapped to a VLAN.
Why wrong: VNI-to-VLAN mapping is needed for Layer 2 forwarding, but the immediate issue is the unreachable source interface.

Full breakdown with real-world context →

Question 8hardmultiple choice

Review the full OSPF breakdown →

After adding a new spine switch to a VXLAN EVPN fabric with OSPF underlay, some leaf switches experience routing instability. Which action could resolve the instability?

A
Increase the OSPF cost on the leaf-to-spine links.
Higher cost makes the new spine less preferred, stabilizing routing.
B
Configure OSPF neighbor authentication.
Why wrong: Authentication adds security but does not affect stability from equal-cost paths.
C
Decrease the OSPF hello timer.
Why wrong: Decreasing hello timer may increase load and worsen instability.
D
Enable OSPF route summarization on the leaves.
Why wrong: Summarization reduces route size but does not prevent flap from equal-cost paths.

Full breakdown with real-world context →

Question 9mediummulti select

Review the full OSPF breakdown →

A network engineer is troubleshooting an OSPF adjacency that fails to reach FULL state between two Nexus 9000 switches. Which TWO are common causes for this issue?

A
Mismatched OSPF process ID
Why wrong: OSPF process ID is local to each router and does not affect adjacency formation.
B
Mismatched area ID
OSPF neighbors must belong to the same area to form an adjacency.
C
Mismatched router ID
Why wrong: Router IDs must be unique, but a mismatch does not prevent adjacency as long as they are unique.
D
Mismatched hello/dead timers
Hello and dead timers must match for OSPF neighbors to form adjacency.
E
Mismatched network type
Why wrong: Network type mismatch does not prevent adjacency; timers can be adjusted to match.

Full breakdown with real-world context →

Question 10mediummultiple choice

Review the full OSPF breakdown →

An engineer is designing a Layer 3 network for a data center using OSPF. The core switches are connected to aggregation switches. To optimize convergence, which OSPF network type should be used on the links between core and aggregation?

A
broadcast
Why wrong: Default type but adds DR election overhead.
B
non-broadcast
Why wrong: Requires manual neighbor commands, not recommended for simple links.
C
point-to-multipoint
Why wrong: Used for hub-and-spoke topologies, not direct links.
D
point-to-point
Eliminates DR election, reduces convergence time.

Full breakdown with real-world context →

Question 11mediummulti select

Review the full OSPF breakdown →

An OSPF router in a broadcast network has not formed a neighbor relationship. What are three possible causes? (Choose three.)

A
Authentication incorrect
Why wrong: Also a possible cause, but not selected here.
B
MTU mismatch
Causes the routers to stay in ExStart state during database exchange.
C
Area ID mismatch
Why wrong: Also a possible cause, but not selected here.
D
Hello interval mismatch
Hello and dead timers must match for adjacency to form.
E
Network type mismatch
Different network types (e.g., broadcast vs point-to-point) can prevent adjacency.

Full breakdown with real-world context →

Question 12easymultiple choice

Review the full OSPF breakdown →

Refer to the exhibit. A network engineer has configured a port-channel for OSPF adjacency. What additional configuration is required for the port-channel to operate correctly?

Exhibit

interface Port-channel10
 no switchport
 ip address 10.1.1.1/30
 ip ospf network point-to-point

A
Set the OSPF priority.
Why wrong: Priority is optional and does not affect basic functionality.
B
No additional configuration needed.
Why wrong: Member interfaces are missing; port-channel is essentially empty.
C
Enable OSPF on the port-channel with `ip router ospf process`.
Why wrong: OSPF is enabled on the interface once the network command covers it.
D
Configure the channel-group mode on member interfaces.
Member interfaces must be assigned to the port-channel using `channel-group`.

Full breakdown with real-world context →

Question 13hardmultiple choice

Review the full OSPF breakdown →

A Nexus switch experiences high CPU utilization due to excessive ICMP traffic. An engineer applies a CoPP policy that includes a class matching ICMP with a drop action. After applying, legitimate OSPF hello packets are also being dropped. What is the most likely cause?

A
The CoPP policy is applied to the wrong interface
Why wrong: CoPP is applied to the control plane, not an interface, so incorrect application is unlikely.
B
The CoPP policy rate-limits all traffic including OSPF below its needed rate
Why wrong: Rate-limiting would still allow some packets; complete dropping of OSPF indicates a drop action, not rate-limit exceed.
C
OSPF packets match the default class which has a drop action
If the default class action is drop, any traffic not explicitly matched (including OSPF) will be dropped. This is a common misconfiguration.
D
The class-map matches multiple protocols including OSPF
Why wrong: If the class-map explicitly matches ICMP via protocol or ACL, it should not match OSPF. However, a poorly designed ACL could cause this.

Full breakdown with real-world context →

Question 14easymultiple choice

Review the full OSPF breakdown →

A data center runs OSPF as the underlay for an EVPN-VXLAN fabric. The fabric includes two spine switches and eight leaf switches. After adding a new leaf switch, the network team notices that some EVPN routes are missing from the other leaves. The new leaf has established BGP EVPN sessions to both spines and the BGP sessions are up. The spines report receiving all routes from the new leaf, but the other leaves do not receive certain prefixes. The engineer checks the BGP configuration on the new leaf and sees the address-family l2vpn evpn is configured under router bgp. Which action should the engineer take to resolve the issue?

A
Check the new leaf's BGP router ID for uniqueness
Why wrong: Duplicate router ID would cause warnings but not missing routes.
B
Verify the new leaf has the address-family l2vpn evpn activated under the neighbor configuration
The address-family must be activated under each neighbor to advertise routes.
C
Ensure the new leaf's BGP next-hop-self is enabled
Why wrong: Next-hop-self is typically applied on route reflectors, not leaves.
D
Verify the cluster ID on the route reflectors is consistent
Why wrong: Cluster ID mismatch does not affect route exchange when sessions are up.

Full breakdown with real-world context →

These 350-601 practice questions are part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style 350-601 questions with detailed explanations, topic-based practice, mock exams, readiness tracking, and study analytics.

OSPF Troubleshooting Scenarios

How to approach ospf troubleshooting scenarios

Quick answer

Related 350-601 topic practice pages

Network practice questions

Compute practice questions

Storage Network practice questions

Automation practice questions

Security practice questions

350-601 fundamentals practice questions

350-601 scenario practice questions

350-601 troubleshooting practice questions

Practice scenarios

Sequence the steps for configuring OSPF on a Cisco Nexus switch in a data center fabric.

A network engineer is configuring OSPF on a Cisco Nexus switch for a data center network. The requirement is to ensure that the switch does not become the Designated Router (DR) on a multi-access segment. Which OSPF configuration achieves this?

A network engineer is troubleshooting an OSPF adjacency issue between two Nexus switches. The neighbors are stuck in the EXSTART state. What is the most likely cause?

A network engineer is configuring OSPF on a pair of Nexus 9000 switches acting as spine switches in a VXLAN fabric. The engineer needs to ensure that the spine switches do not become the DR for any VLAN. Which configuration should be applied?

During a network upgrade, an engineer applies a new OSPF configuration on a Nexus 9000 spine. After the change, several leaf switches lose connectivity to each other. The engineer examines the logs and sees OSPF adjacency flapping. What is the most likely cause?

Refer to the exhibit. An engineer configured a VXLAN tunnel endpoint (VTEP) but the VXLAN tunnel is not operational. The underlay OSPF adjacency is established. What is the missing configuration?

Exhibit

After adding a new spine switch to a VXLAN EVPN fabric with OSPF underlay, some leaf switches experience routing instability. Which action could resolve the instability?

A network engineer is troubleshooting an OSPF adjacency that fails to reach FULL state between two Nexus 9000 switches. Which TWO are common causes for this issue?

An engineer is designing a Layer 3 network for a data center using OSPF. The core switches are connected to aggregation switches. To optimize convergence, which OSPF network type should be used on the links between core and aggregation?

An OSPF router in a broadcast network has not formed a neighbor relationship. What are three possible causes? (Choose three.)

Refer to the exhibit. A network engineer has configured a port-channel for OSPF adjacency. What additional configuration is required for the port-channel to operate correctly?

Exhibit

A Nexus switch experiences high CPU utilization due to excessive ICMP traffic. An engineer applies a CoPP policy that includes a class matching ICMP with a drop action. After applying, legitimate OSPF hello packets are also being dropped. What is the most likely cause?