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VMware 3V0-25.25 Exam Questions
VMware Cloud Foundation 9.0 Networking (Page 2 )

Updated On: 24-Feb-2026
Page 2 of 13
PDF with 60 Questions

An administrator has noticed an issue in a freshly deployed VMware Cloud Foundation (VCF) environment where the BGP neighborship between the Tier-0 gateway and a physical router remains in the Idle state. Pings between the uplink IPs are successful.
What is the issue?

  1. Autonomous System number mismatch.
  2. Distributed Firewall blocking traffic.
  3. Geneve tunnel down.
  4. Overlay MTU too low.

Answer(s): A

Explanation:

Comprehensive and Detailed 250 to 350 words of Explanation From VMware Cloud Foundation (VCF) documents:

In the context of VMware Cloud Foundation (VCF), particularly versions 5.x and the architectural advancements in VCF 9.0, the establishment of North-South routing via the NSX Tier-0 Gateway is a critical post-deployment or bring-up task. The Tier-0 gateway uses Border Gateway Protocol (BGP) to peer with physical Top-of-Rack (ToR) switches to exchange reachability information for the overlay networks.

When a BGP session is reported in the "Idle" state, it indicates that the BGP Finite State Machine (FSM) is at its first stage and is not yet attempting a TCP connection, or it has encountered an error that forced it back to this state. According to VMware VCF documentation and NSX troubleshooting guides, if the administrator can successfully ping between the Tier-0 uplink IP and the physical router interface, Layer 3 reachability is confirmed. This eliminates issues related to physical cabling, VLAN tagging on the trunk ports, or basic IP interface configuration.

The primary reason a BGP session remains Idle despite successful ICMP reachability is a configuration mismatch. Specifically, an Autonomous System (AS) number mismatch is the most frequent culprit. BGP requires that the "Remote AS" configured on the Tier-0 gateway matches the "Local AS" of the physical peer. If the SDDC Manager automated workflow or the manual configuration in NSX Manager contains a typo in these values, the protocol handshake will fail immediately.

While a Distributed Firewall (DFW) could technically block port 179, it is not common in a "freshly deployed" environment for the default rules to block the Edge Node's control plane traffic. Geneve tunnels and MTU issues (Option C and D) typically affect the data plane--causing packet loss for encapsulated guest VM traffic--but they do not prevent the BGP control plane (running over standard TCP) from moving beyond the Idle state. Therefore, verifying the AS numbers in the VCF Planning and Preparation Workbook against the physical switch configuration is the verified resolution path.



A cloud service provider runs VPCs with differing traffic patterns:

· Some VPCs are generating high, large North/South flows.

· Most of the VPCs generate very little traffic.

The architect needs to optimize Edge dataplane resource consumption while ensuring that noisy VPCs do not impact others.

Which optimization satisfies the requirement?

  1. Assign one dedicated Edge node per high-traffic VPC.
  2. Reduce the number of VPCs by consolidating VPCs into shared namespaces.
  3. Convert high-traffic VPCs into VLAN-backed segments attached directly to Tier-0 gateways.
  4. Use multiple Edge clusters and distribute VRF-backed VPCs based on traffic profiles.

Answer(s): D

Explanation:

Comprehensive and Detailed 250 to 350 words of Explanation From VMware Cloud Foundation (VCF) documents:

In a VMware Cloud Foundation (VCF) environment, especially with the architectural evolution in VCF 9.0, the Virtual Private Cloud (VPC) model is the primary way to deliver self-service, isolated networking. The networking performance for North/South traffic--traffic leaving the SDDC for the physical network--is processed by NSX Edge Nodes. These Edge Nodes use DPDK (Data Plane Development Kit) to provide high-performance packet processing, but their resources (CPU and Memory) are finite.

When dealing with "noisy neighbors"--tenants or VPCs that consume a disproportionate amount of throughput--it is critical to isolate their data plane impact. According to the VMware Validated Solutions and VCF Design Guides, the most scalable and efficient way to achieve this is through the use of Multiple Edge Clusters. By creating distinct Edge clusters, an architect can physically isolate the compute resources used for routing.

In this scenario, high-traffic VPCs can be backed by specific VRF (Virtual Routing and Forwarding) instances on a Tier-0 gateway that is hosted on a dedicated high-performance Edge Cluster. Meanwhile, the numerous low-traffic VPCs can share a different Edge Cluster. This "Traffic Profile" based distribution ensures that a spike in traffic within a "heavy" VPC only consumes the DPDK cycles of its assigned Edge nodes, leaving the resources for the "quiet" VPCs untouched.

Option A is incorrect because Edge nodes function in clusters for high availability; assigning a single node creates a single point of failure and is administratively heavy. Option B reduces the multi- tenancy benefits and doesn't solve the resource contention at the Edge level. Option C removes the benefits of the software-defined overlay and VPC consumption model. Therefore, distributing VRF- backed VPCs across multiple Edge clusters based on their expected load is the verified design best practice for optimizing resource consumption while maintaining strict performance isolation in a VCF provider environment.



A large multinational corporation is seeking proposals for the modernization of a Private Cloud environment. The proposed solution must meet the following requirements:

· Support multiple data centers located in different geographic regions.

· Provide a secure and scalable solution that ensures seamless connectivity between data centers and different departments.

Which three NSX features or capabilities must be included in the proposed solution? (Choose three.)

  1. NSX Edge
  2. AVI Load Balancer
  3. vDefend
  4. Virtual Private Cloud (VPC)
  5. Centralized Network Connectivity
  6. NSX L2 Bridging

Answer(s): A,C,D

Explanation:

Comprehensive and Detailed 250 to 350 words of Explanation From VMware Cloud Foundation (VCF)

documents:

In a modern VMware Cloud Foundation (VCF) architecture, particularly when addressing the needs of a multinational corporation with geographically dispersed data centers, the solution must prioritize multi-tenancy, security, and consistent delivery. The integration of NSX within VCF provides these core pillars.

First, the NSX Edge is a foundational requirement for any multi-site or modern cloud environment. It serves as the bridge between the virtual overlay network and the physical world. In a multi-region deployment, NSX Edges facilitate North-South traffic and are essential for supporting features like Global Server Load Balancing (GSLB) or site-to-site connectivity. Without the Edge, the software-

defined data center (SDDC) cannot communicate with external networks or peer via BGP with physical routers.

Second, vDefend (formerly known as NSX Security) provides the advanced security framework required for a "secure and scalable" environment. This includes Distributed Firewalling (DFW), Distributed IDS/IPS, and Malware Prevention. For a corporation with different departments, vDefend allows for micro-segmentation, ensuring that a security breach in one department's segment cannot move laterally to another. This is critical for meeting compliance and isolation requirements across global regions.

Third, the Virtual Private Cloud (VPC) model is the cornerstone of the latest VCF 9.0 and 5.x architectures. It enables the "scalable solution" for different departments by providing a self-service consumption model. Each department can manage its own isolated network space, including subnets and security policies, without needing deep networking expertise or constant tickets for the central IT team. This abstraction simplifies management across multiple data centers and allows for consistent application of policies regardless of the physical location.

While AVI Load Balancer and Centralized Network Connectivity are valuable, they are often considered add-ons or outcomes rather than the core architectural features that define the multi- tenant, secure, and geographically distributed nature of a modern VCF private cloud modernization project.



An administrator is troubleshooting why workloads in NSX cannot reach the external network 10.100.0.0/16. The Tier-0 Gateway is in Active/Active mode and has the following configuration:

· Uplink-1 (VLAN 100): 192.168.100.0/24 -> router R1 at 192.168.100.1

· Uplink-2 (VLAN 101): 192.168.101.0/24 -> router R2 at 192.168.101.1

· A static route for 10.100.0.0/16 was added with both next-hops (192.168.100.1 and 192.168.101.1).

· The Scope of this route is set to Uplink-1.

Symptoms:

· Virtual Machines (VMs) cannot reach 10.100.0.0/16

· Traceroute from the VM stops at the Tier-0 gateway with "Destination Net Unreachable"

· Pings from the Edge nodes to both 192.168.100.1 and 192.168.101.1 are success

What explains why workloads in NSX cannot reach the external network?

  1. Static routes do not support Equal Cost Multi-Pathing (ECMP) in NSX.
  2. The static route Scope is set to only one uplink interface, but the next-hops are on two different VLANs.
  3. The next-hops should have been configured as the Tier-0's own uplink IPs instead of the routers IPs.
  4. The physical routers are missing return routes.

Answer(s): B

Explanation:

Comprehensive and Detailed 250 to 350 words of Explanation From VMware Cloud Foundation (VCF) documents:

Troubleshooting routing in a VMware Cloud Foundation (VCF) environment requires a deep understanding of how the NSX Tier-0 Gateway processes forwarding entries. In an Active/Active configuration, the Tier-0 gateway is designed to utilize ECMP (Equal Cost Multi-Pathing) to distribute traffic across multiple paths to the physical network.

The specific failure described--where a traceroute fails at the Tier-0 with "Destination Net Unreachable" despite the Edge nodes having basic ping connectivity to the routers--points toward a routing table entry error rather than a physical connectivity issue. In NSX, when a static route is created, an administrator has the option to set a "Scope." The Scope explicitly tells the NSX routing engine which interface should be used to reach the defined next-hops.

In this scenario, the administrator has defined two next-hops (R1 and R2) but has restricted the scope of the static route to Uplink-1 only. Because R2 (192.168.101.1) is on a different subnet/VLAN (VLAN 101) that is associated with Uplink-2, the Tier-0 gateway cannot resolve the next-hop for R2 via Uplink-1. Furthermore, if the gateway detects an inconsistency between the defined next-hop and the scoped interface, it may invalidate the route or fail to install it correctly in the forwarding information base (FIB) for the service router.

According to VMware documentation, the Scope should typically be left as "All Uplinks" or carefully matched to the interfaces that have Layer 2 reachability to the next-hop. By scoping it to only Uplink- 1, the router R2 becomes unreachable for that specific route entry. Even for R1, if the hashing mechanism of the Active/Active Tier-0 attempts to use a component of the gateway not associated with that scope, the traffic will fail. The error "Destination Net Unreachable" at the Tier-0 hop confirms that the Tier-0 has no valid, functional path in its routing table for the 10.100.0.0/16 network due to this scoping conflict.



An administrator is investigating packet loss reported by workloads connected to VLAN segments in an NSX environment. Initial checks confirm:

· All VMs are powered on

· VLAN segment IDs are consistent across transport nodes

· Physical switch configurations are correct.

Which two NSX tools can be used to troubleshoot packet loss on VLAN Segments? (Choose two.)

  1. Flow Monitoring
  2. Traceflow
  3. Packet Capture
  4. Activity Monitoring
  5. Live Flow

Answer(s): B,C

Explanation:

Comprehensive and Detailed 250 to 350 words of Explanation From VMware Cloud Foundation (VCF) documents:

In a VMware Cloud Foundation (VCF) environment, troubleshooting packet loss requires tools that can provide visibility into both the logical and physical paths of a packet.
When dealing specifically with VLAN segments (as opposed to Overlay segments), the traffic does not leave the host encapsulated in Geneve; instead, it is tagged with a standard 802.1Q header.

Traceflow is the primary diagnostic tool within NSX for identifying where a packet is being dropped. It allows an administrator to inject a synthetic packet into the data plane from a source (such as a VM vNIC) to a destination. The tool then reports back every "observation point" along the path, including switching, routing, and firewalling. If a packet is dropped by a Distributed Firewall (DFW) rule or a physical misconfiguration that wasn't caught initially, Traceflow will explicitly state at which stage the packet was lost.

Packet Capture is the second essential tool. NSX provides a robust, distributed packet capture utility that can be executed from the NSX Manager CLI or UI. This tool allows administrators to capture traffic at various points, such as the vNIC, the switch port, or the physical uplink (vmnic) of the ESXi Transport Node. By comparing captures from different points, an administrator can determine if a packet is reaching the virtual switch but failing to exit the physical NIC, or if return traffic is reaching the host but not the VM.

Options like Flow Monitoring and Live Flow are excellent for observing traffic patterns and session statistics (IPFIX), but they are less effective for pinpointing the exact cause of "packet loss" compared to the granular, packet-level analysis provided by Traceflow and Packet Capture. Activity Monitoring is typically used for endpoint introspection and user-level activity, which is irrelevant to Layer 2/3 packet loss troubleshooting.






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