350-401 Virtual Machines and Hypervisors Practice Questions

Question 1

A network engineer is deploying a new virtualized application on a VMware vSphere cluster. The application requires dedicated CPU cores to meet licensing requirements, and the engineer must ensure that no other virtual machine can use those cores. The cluster uses VMware ESXi 7.0. Which configuration should the engineer apply to the virtual machine?

Accepted Answer

Configure CPU affinity to pin the VM to specific physical cores.. CPU affinity (option A) is the correct configuration because it explicitly binds a virtual machine's vCPUs to specific physical cores, ensuring that no other VM can use those cores. This meets the licensing requirement for dedicated CPU cores by preventing co-scheduling or sharing of those physical cores with other workloads, which CPU reservation alone does not guarantee.

Answer

Set a CPU reservation equal to the number of vCPUs.

Answer

Enable NUMA node affinity for the VM.

Answer

Configure a CPU limit equal to the number of vCPUs.

Question 2

An enterprise is migrating a legacy application from a physical server to a virtual machine on a KVM-based hypervisor. The application requires direct access to a PCIe network interface card for performance reasons. The engineer needs to provide the VM with dedicated hardware access while maintaining isolation from other VMs. Which technology should the engineer use?

Accepted Answer

Use PCI passthrough to assign the NIC directly to the VM.. PCI passthrough (Option A) is correct because it assigns the entire physical PCIe NIC directly to the VM, giving it exclusive, dedicated hardware access with full performance and no hypervisor overhead. This meets the requirement for direct access while maintaining isolation, as other VMs cannot use the same device.

Answer

Enable SR-IOV and assign a virtual function to the VM.

Answer

Configure a paravirtualized network driver (virtio).

Answer

Attach the VM to a Linux bridge using macvtap.

Question 3

A network engineer is troubleshooting performance issues on a VMware ESXi host running multiple VMs. The host has two physical CPUs, each with 8 cores (16 logical processors with Hyper-Threading enabled). One VM, configured with 8 vCPUs, experiences high CPU ready time. Other VMs on the host are idle. What is the most likely cause of the high CPU ready time?

Accepted Answer

The VM's vCPUs span multiple NUMA nodes, causing memory access delays.. The VM has 8 vCPUs, but each physical CPU has only 8 cores (16 logical processors with Hyper-Threading). Since a single NUMA node typically corresponds to one physical CPU socket, an 8-vCPU VM cannot fit entirely within one NUMA node if the VM's vCPUs exceed the number of physical cores on that socket (8 cores). The hypervisor must span the VM across both NUMA nodes, causing remote memory access and increasing CPU ready time due to NUMA latency.

Answer

Hyper-Threading is disabled on the ESXi host.

Answer

The host is overcommitted with too many vCPUs.

Answer

The VM has more vCPUs than physical cores on a single socket.

Question 4

A company is deploying a virtualized firewall on a VMware ESXi host. The firewall VM requires high network throughput and low latency. The engineer decides to use SR-IOV to assign a virtual function (VF) from a physical NIC to the VM. After configuration, the VM can communicate, but the host's management network becomes unreachable. What is the most likely cause?

Accepted Answer

The physical NIC's PF is also used for the host management network, and SR-IOV configuration disrupted it.. When SR-IOV is enabled on a physical NIC, the Physical Function (PF) is shared between the host management network and the Virtual Functions (VFs). If the PF is used for the host management network, enabling SR-IOV can disrupt the PF's driver or configuration, causing the management network to become unreachable. This is a common misconfiguration where the same NIC is used for both management and SR-IOV VFs.

Answer

The VM's VF is using the same MAC address as the host management interface.

Answer

The ESXi host requires a dedicated physical NIC for management when using SR-IOV.

Answer

The VM's VF is consuming all available bandwidth on the NIC.

Question 5

A network engineer is designing a disaster recovery solution using VMware vSphere. The engineer needs to replicate virtual machines from the primary site to a secondary site with minimal downtime. The application VMs are running on NFS datastores. The engineer plans to use vSphere Replication. What prerequisite must be met for vSphere Replication to work with NFS datastores?

Accepted Answer

The NFS datastores must be mounted on both the source and target ESXi hosts.. vSphere Replication operates at the hypervisor level, replicating VM data from the source ESXi host to the target ESXi host. For NFS datastores, the source and target hosts must each have the NFS datastore mounted because vSphere Replication reads the VM files from the source NFS mount and writes them to the target NFS mount. Without both mounts, the replication engine cannot access the source data or place the replica on the target storage.

Answer

The NFS datastores must be backed by a storage array that supports snapshot offloading.

Answer

The VMs must be configured with thick provisioning eager zeroed disks.

Answer

The NFS datastores must be part of a vSAN cluster.

Question 6

An engineer is deploying a Linux virtual machine on a KVM hypervisor. The VM needs to be connected to a virtual network that provides isolation from other VMs on the same host but allows communication with the host and external networks. The engineer creates a Linux bridge and attaches the VM's tap interface to it. However, the VM cannot reach the external network. The host has a physical NIC (eth0) connected to the corporate network. What is the missing configuration step?

Accepted Answer

Add the physical NIC (eth0) as a port to the Linux bridge.. A Linux bridge acts like a virtual switch. To allow the VM to reach the external network, the physical NIC (eth0) must be added as a port to the bridge. This bridges the VM's tap interface with the host's physical network, enabling Layer 2 connectivity to the corporate network and upstream routing.

Answer

Configure a default gateway on the VM's network interface.

Answer

Assign an IP address to the Linux bridge interface.

Answer

Enable IP forwarding and configure NAT on the host.

Question 7

A network engineer is troubleshooting a VMware vSphere cluster where a VM with a large memory footprint (256 GB) is experiencing poor performance. The host has two NUMA nodes, each with 128 GB of memory. The VM is configured with 256 GB of memory and 4 vCPUs. Performance monitoring shows high memory latency and CPU ready time. What is the most likely cause?

Accepted Answer

The VM's memory size forces it to span multiple NUMA nodes, increasing memory access latency.. The VM is configured with 256 GB of memory, but each NUMA node on the host has only 128 GB. Since a single NUMA node cannot satisfy the VM's memory allocation, the hypervisor must split the VM across both NUMA nodes. This forces memory accesses to cross the NUMA interconnect (e.g., QPI or UPI), which introduces significantly higher latency compared to local memory access, directly causing the observed high memory latency and increased CPU ready time.

Answer

The VM has too few vCPUs for the memory size.

Answer

The host is using memory ballooning to reclaim memory from other VMs.

Answer

The host's memory is overcommitted.

Question 8

An engineer is configuring a virtual machine on a Microsoft Hyper-V host. The VM runs a legacy application that requires a static MAC address. The engineer sets the MAC address in the VM settings. After the VM starts, the application cannot communicate on the network. The engineer verifies that the MAC address is not duplicated on the network. What is the most likely cause?

Accepted Answer

The static MAC address is not within the allowed range for Hyper-V virtual machines.. Hyper-V enforces a specific range for static MAC addresses assigned to virtual machines. The default allowed range is 00-15-5D-XX-XX-XX, derived from the Microsoft Organizationally Unique Identifier (OUI). If the engineer configured a MAC address outside this range (e.g., starting with a different OUI), Hyper-V will not allow the VM to use it, effectively breaking network communication even though the address is not duplicated on the network.

Answer

The VM is configured to use a dynamic MAC address, overriding the static setting.

Answer

The VM's network adapter is set to use the legacy network adapter type.

Answer

The VM is a generation 2 VM, which does not support static MAC addresses.

Question 9

A network engineer is migrating a physical server running a critical database to a virtual machine on a VMware vSphere cluster. The database requires high I/O performance and low latency. The engineer decides to use VMFS datastores with multiple extents to improve performance. After migration, the database performance is worse than on the physical server. What is the most likely reason?

Accepted Answer

VMFS datastores with multiple extents can cause I/O to span multiple LUNs, increasing latency.. VMFS datastores with multiple extents distribute data across multiple LUNs, which can cause I/O operations to span physical storage devices. This introduces additional latency due to the need for coordination across LUNs, negating the performance benefit expected from a single, contiguous LUN. For a database requiring high I/O and low latency, this spanning effect degrades performance compared to a physical server with direct-attached storage.

Answer

The VMFS datastore does not support files larger than 2 TB.

Answer

The virtual disk is configured as thin provisioned, causing write amplification.

Answer

The virtual disk is configured as thick eager zeroed, causing slow initial writes.

Question 10

A company is deploying a multi-tenant data center using VMware vSphere. The architect must ensure that each tenant’s virtual machines (VMs) are isolated at Layer 2 while sharing the same physical NICs. Which design approach best meets this requirement?

Accepted Answer

Configure a single standard virtual switch and assign each VM to a separate port group with unique VLAN IDs.. Option A is correct because configuring a standard virtual switch with separate port groups and unique VLAN IDs provides Layer 2 isolation between tenants by leveraging 802.1Q VLAN tagging. Each VM’s traffic is tagged with its assigned VLAN ID, ensuring that VMs in different port groups cannot communicate directly at Layer 2, even though they share the same physical NICs.

Answer

Deploy a separate physical NIC for each tenant and bridge them to the VMs.

Answer

Use a distributed virtual switch with VLAN trunking and assign all VMs to the same port group.

Answer

Enable promiscuous mode on the virtual switch to allow all VMs to see each other’s traffic.

Virtual Machines and Hypervisors