Troubleshooting Inaccessible Synology iSCSI Targets Following ESXi Reinstallation or Network Re-IP

Products

• VMware vSphere ESXi

Issue/Introduction

 

• ESXi host cannot see the Synology iSCSI LUN in the Devices list.

• Unable to create a new VMFS datastore.

• Other hosts in the same cluster see the LUN without issue.

 

 

Environment

vSphere 8.x

Cause

Synology Binding was customized for specific interfaces

When a Synology NAS has iSCSI Binding customized, it means the iSCSI service is restricted to listening only on specific physical or virtual network interfaces (e.g., LAN 3 and LAN 4).

If you reinstalled your ESXi host and changed management/vSAN IPs, you likely moved the storage traffic to a subnet or physical path that the Synology is explicitly ignoring.

Resolution

Change the network binding and allow  all network  interfaces on Synology interface.

By default, Synology may be configured to only allow iSCSI traffic on specific LAN ports (e.g., only your 10GbE ports). To resolve "Target Not Found" errors after an ESXi reinstall, we will set the NAS to listen on all available interfaces.

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Step-by-Step Configuration

1. Access SAN Manager

1. Log into your Synology DSM (DiskStation Manager).

2. Open the Main Menu and launch SAN Manager.

3. In the left-hand sidebar, click on Settings.

2. Modify Network Binding

1. Look for the Network Binding section.

2. Click the Edit button (or the Global Setting toggle depending on your DSM version).

3. Select the radio button for "All Interfaces".

   • Alternatively, if you prefer manual control, ensure every LAN port connected to your storage switch is checked.

4. Click OK or Apply.

To Verify the LUN availability and ESXI initiator login follow below steps.

1. On the ESXi host, run a Storage Adapter Rescan.
2. Check esxcli storage core device list to see if the Synology LUN now appears.
3. Check the Synology Log Center to confirm successful login from the ESXi initiator IP.
   
   
4. Screenshots for reference.