Error: iSCSI LUN or datastore discovery failure despite updated static targets

Products

VMware vCenter Server

Issue/Introduction

Symptoms:

iSCSI datastores are visible and mounted on some hosts in a cluster but missing on others.
Static discovery targets are populated, but LUNs do not appear in the storage view.
vmkernel.log shows iSCSI login timeouts or connection failures to storage target IPs.
The target LUNs do not appear in the Devices list even after performing a rescan of the storage adapter and devices.
A vmkping from the affected ESXi host to the iSCSI target IP addresses results in 100% packet loss.
vmkping -I vmk# -s 1472 -d 10.#.#.#
PING 10.#.#.# (10.#.#.#): 1472 data bytes
--- 10.#.#.# ping statistics ---
3 packets transmitted, 0 packets received, 100% packet loss
The MTU configured is uniform and there is no mismatch
The /var/run/log/vobd.log file on the affected host shows network communication or connectivity failures.
2026-01-08T07:00:00.479Z In(14) vobd[2097717]: [iscsiCorrelator] 1012308076493us: [esx.problem.storage.iscsi.target.connect.error] Login to ISCSI target iqn.1992####################### on vmhba64 @ vmk# failed. The ISCSI initiator could not establish a network connection to the target.
2026-01-08T07:00:00.479Z In(14) vobd[2097717]: The event ([esx.problem.storage.iscsi.target.connect.error] Login to iSCSI target iqn.1992####################### on vmhba64 @ vmk# failed. The iSCSI initiator could not establish a network connection to the target.) was sent immediately to hostd;
2026-01-08T07:00:09.246Z In(14) vobd[2097717]: [iscsiCorrelator] 1012336916836us: [vob.iscsi. target.connect.error] vmhba64 @ vmk# failed to login to iqn.1992####################### because of a network connection failure.

Environment

VMware ESXi 8.x

VMware ESX 9.x

Cause

This issue occurs due to Layer 2 network connectivity failures between the ESXi host and the storage array. Common triggers include missing VLAN tags on physical switch ports, MTU mismatches (Jumbo Frames configuration), or storage array ACL/Masking updates.

Cause Validation:

On working hosts, vmkping to the iSCSI targets is successful with 0% loss. On non-working hosts, the same test fails completely.
From the vmkernel interface configuration, it is observed that on both working and non-working ESXi hosts, the vmkernel interface has VLAN configured.
For example, in the below screenshot, vmk3 interface is used for iscsi connectivity and there is a VLAN tagging.
On the working ESXi hosts, the physical adapters do not have any specific VLAN tagging or restriction. However, on the non working ESXi host, there is VLAN tagging at the physical switch and this does not allow the traffic through VLAN1
Non working host:
Also, on reviewing the VLAN stats, on the problematic ESXi host, there are no packets received for the VLAN1
esxcli network nic vlan stats get -n vmnic#
VLAN 1
Packets received: 0
Packets sent: 3

Resolution

Perform the following troubleshooting steps to restore connectivity:

Verify Physical Network Configuration: Ensure the physical switch ports connected to the iSCSI VMkernel adapters are configured with the correct VLAN IDs and MTU settings.
Validate MTU Consistency: Check that the MTU is consistent (e.g., 9000 for Jumbo Frames) across the VMkernel adapter, Virtual Switch, and physical network path.
Test Connectivity with vmkping: Run the following commands from the ESXi CLI to test connectivity to the storage target IPs (####):
- Standard frames: vmkping -I vmk# -d -s 1472 [Target_IP]
- Jumbo frames: vmkping -I vmk# -d -s 8972 [Target_IP] vmk# Configured vmkernel port for iSCSI Traffic
Perform Storage Rescan: Perform a manual storage rescan using the vSphere Client or the command: esxcli storage core adapter rescan --all.
Verify Storage Array ACLs: Confirm with the storage vendor that the Host Initiator IQN is correctly mapped in the storage array’s ACL or Masking views.

Additional Information

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