VMware 2V0-15.25 Exam Dumps

In a vSAN Stretched Cluster, communication between the witness node and data nodes requires several specific TCP/UDP ports. The ability to successfully execute:

vmkping -I <witness-vmk> <vsan-IP> -s 1472 -d

confirms that:

L2/L3 connectivity is present

MTU is correctly configured

ICMP traffic flows without fragmentation

However, vmkping alone does not verify vSAN control-plane communication.

For the vSAN Witness to properly form a cluster, TCP port 12321 must be open bidirectionally between:

Witness Data nodes

Data nodes Witness

Port 12321 is required for:

vSAN cluster membership

Witness traffic

vSAN object health/state synchronization

If this port is blocked by firewall policy or misconfigured network ACLs, the nodes can ping each other, but vSAN witness traffic will fail, preventing the stretched cluster from forming.

Why the other options are incorrect:

B . Port 443 --- Required for management, not cluster formation.

C . No VMs in cluster --- Has no impact on witness formation.

D . Jumbo frames not enabled --- Already ruled out by the successful 1472-byte vmkping with DF bit.

In VMware Cloud Foundation 9.0, using vSAN Express Storage Architecture (ESA) with Auto-Policy Management, the system automatically selects the correct storage policy based on the cluster size and desired failure protection. When the administrator configures tolerance for a single failure (FTT=1 using RAID-1 mirroring), vSAN ESA requires sufficient remaining hosts during a failure event to reprotect objects.

A minimum of 3 ESA-capable hosts is required for RAID-1, and re-protection after a failure requires enough hosts with available capacity to place new replica components. In small ESA clusters (e.g., 3 or 4 nodes), if one host fails, the remaining hosts may not meet the placement rules for automatic rebuild to restore compliance. ESA enforces strict placement rules to maintain consistent performance and resilience; if vSAN determines that object layout compliance cannot be restored without violating these rules, it enters Reduced availability with no rebuild state.

This behavior is expected and documented: rebuilds cannot occur if the cluster does not have sufficient hosts or free capacity to recreate absent components. The administrator's ESA configuration behaved correctly given the cluster size limitation, making B the correct answer.

Application Monitoring in VCF Operations uses Telegraf agents running inside virtual machines. These agents forward metrics to the Cloud Proxy, which then sends them to the Operations analytics cluster. One of the most common reasons an agent stops reporting data---especially exactly 24 hours after deployment---is clock drift or time mismatch between the VM (running the Telegraf agent) and the Cloud Proxy.

VCF Operations enforces strict timestamp validation. If the timestamps from the agent are outside the acceptable drift window, the Cloud Proxy rejects incoming data as invalid. In this case, the Telegraf agents appear installed and functional, but no new metrics are received by the analytics engine.

This is a well-known issue documented in VMware Aria/VCF Operations agent-based monitoring, where:

Agents send metrics with local system time.

Cloud Proxy enforces time validation to prevent corrupt metric ingestion.

A drift >5 minutes commonly results in zero data collection despite healthy connectivity.

Options B and C cannot stop data flow after exactly 24 hours; they would prevent initial collection. Option D (virtual hardware/tools compatibility) affects VM operations but not Telegraf metric time-stamp validation.

In VMware Cloud Foundation 9.0, supplemental storage such as NFS is fully supported for workload domains when configured correctly. When an NFS datastore mounts successfully in vSphere but users cannot write data, the issue almost always lies in the export permissions on the NFS server. vSphere will allow mounting a read-only NFS export, but write operations will fail silently at the VM or guest OS level.

VCF documentation confirms that ESXi requires explicit read/write export permissions, typically configured per-host or by IP subnet, on the NFS server. Even if network connectivity and VM-level access appear healthy, incorrect server-side permissions prevent ESXi from executing write operations.

Option A is incorrect because NFS servers are not validated by the HCL for write capability. Option B (rebooting the host) is unnecessary and unrelated to permission enforcement. Option D (MTU mismatch) may cause performance issues, not write-access failures.

Thus, the next troubleshooting step is to verify that the ESXi hosts have read/write access on the NFS share, making C the correct answer.

To diagnose and resolve the intermittent performance and connection drop issues with the supplemental iSCSI storage, the administrator should focus on network layer consistency and health, particularly regarding packet size (MTU) and delivery (TCP).

Examine the iSCSI VMkernel port for TCP retransmissions (Action B - Diagnose): 'Intermittent' connection drops and slow I/O are classic symptoms of packet loss or fragmentation issues. By examining the ESXi network stats (e.g., using esxtop key n or viewing vSphere performance charts) for TCP retransmissions, the administrator can confirm if packets are being dropped or lost in transit. Checksum offload errors can also indicate issues where the NIC hardware is incorrectly validating packets, causing the OS to drop them. This step identifies the root cause (packet loss/corruption).

Ensure all ESX hosts have the VMkernel port MTU set to 9000 (Action E - Resolve): For high-performance storage traffic like iSCSI in a VMware Cloud Foundation environment, it is best practice to use Jumbo Frames (MTU 9000) end-to-end (Host -> Switch -> Storage Array).

The symptom that some hosts are affected suggests configuration drift where those specific hosts might be set to a different MTU (e.g., 1500) or are mismatched with the physical network/target (which is likely set to 9000 for performance).

An MTU mismatch (e.g., Target sending 9000-byte frames to a Host/Switch expecting 1500) typically results in the 'Do Not Fragment' (DF) bit causing packet drops, leading to the reported connection drops and retransmission delays. Ensuring a consistent MTU of 9000 across the fleet resolves this and aligns with VCF performance standards.

Note: Option A (CHAP) is for authentication security, not performance. Option C (Update network plugin) is a lifecycle task but less likely to be the immediate fix for 'some hosts' having intermittent drops compared to the common issue of MTU mismatch. Option D (MTU 1500) would resolve drops if the physical network doesn't support Jumbo Frames, but would degrade performance, making E the preferred resolution for a 'performance' storage tier.