VMware ESXi and vSphere Cluster Management

iSCSI Naming and Addressing in VMware ESXi

Learn how ESXi iSCSI initiators and targets use IQN and EUI names, compare both formats, and find an ESXi software iSCSI adapter name in vSphere.

Why iSCSI Nodes Need Names

An iSCSI node is an entity that participates in iSCSI communication. The two main node types are an iSCSI initiator and an iSCSI target.

  • An initiator is the client-side component that starts iSCSI sessions. On ESXi, this is commonly a software iSCSI adapter or another iSCSI-capable storage adapter.
  • A target is the storage-side component that presents storage resources, such as logical units, to initiators.

Each iSCSI node requires a unique iSCSI name. This name is a persistent identity for the node and is separate from its network address.

Separating identity from addressing is important because an initiator or target can change IP addresses, use multiple network paths, or be reached through different interfaces while retaining the same node identity. Storage access controls can therefore identify a host by its iSCSI name instead of relying only on an IP address.

iSCSI Qualified Names

An iSCSI Qualified Name, or IQN, is one standard format for naming iSCSI initiators and targets.

iqn.yyyy-mm.naming-authority:unique-name
  • iqn is the required prefix identifying the IQN format.
  • yyyy-mm records the year and month when the naming authority was established.
  • naming-authority identifies the organization responsible for the namespace. It commonly uses reverse-domain notation, such as com.example.
  • unique-name is an organization-defined name that distinguishes this node from other nodes in the same relevant environment.

The complete IQN must be unique within the relevant iSCSI environment. A naming authority should assign node names systematically so that initiators and targets do not receive duplicate identities.

IQN Example

iqn.1992-08.com.vmware:host-1

Prefix — iqn identifies the IQN naming format.

Naming authority date — 1992-08 records when the naming authority was established.

Naming authority — com.vmware uses reverse-domain notation.

Unique node name — host-1 is the organization-selected identifier for this node.

The date in an IQN is not the date the ESXi host or storage array was installed. It describes the establishment date associated with the naming authority.

Enterprise Unique Identifier Names

Enterprise Unique Identifier, or EUI, is the second standard iSCSI naming format covered here.

eui.16-hex-digits

The eui prefix identifies the format. The remaining value is a textual representation of a 64-bit IEEE EUI identifier and must contain exactly 16 hexadecimal digits.

A hexadecimal digit is a base-16 character from 0 through 9 or A through F. Because each hexadecimal digit represents four bits, 16 hexadecimal digits represent 64 bits.

eui.5412369875AACDAF
  • The name begins with the eui prefix.
  • 5412369875AACDAF contains exactly 16 hexadecimal digits.
  • The value represents a 64-bit IEEE EUI-based identifier.

Conceptually, the 64-bit identifier is divided into two allocation areas:

  • The first 24 bits identify the IEEE-assigned company identifier.
  • The final 40 bits identify a unique value assigned by that organization.

Company identifier — 24 bits — Identifies the company assigned the EUI namespace by IEEE.

Organization-assigned unique identifier — 40 bits — Distinguishes the specific value assigned within that company namespace.

IQN and EUI Compared

IQN — General syntax: iqn.yyyy-mm.naming-authority:unique-name — Identity source: naming authority and organization-defined node name — Key characteristics: structured, readable, and variable in its descriptive portions — Example: iqn.1992-08.com.vmware:host-1

EUI — General syntax: eui.16-hex-digits — Identity source: a 64-bit IEEE EUI allocation — Key characteristics: fixed hexadecimal representation with 16 hexadecimal digits — Example: eui.5412369875AACDAF

Both formats provide unique identifiers for iSCSI initiators and targets. IQNs communicate organizational ownership and a readable node label. EUIs provide a fixed-length hexadecimal representation of an IEEE-based identifier.

The storage or iSCSI implementation determines which format is used. Record the name exactly as displayed or assigned. The prefix, punctuation, capitalization where applicable, digits, and unique portion can all matter during target access control and host identification.

Find an ESXi iSCSI Adapter Name in the vSphere Web Client

The iSCSI name shown for an ESXi adapter is commonly the value a storage administrator needs when identifying or authorizing the host on an iSCSI target.

  1. Select the ESXi host in the vSphere inventory.
  2. Open Manage for the selected host.
  3. Open the Storage area.
  4. Select Storage Adapters.
  5. Choose the applicable software iSCSI adapter.
  6. Review the adapter status information and locate its iSCSI name.
  7. Record the displayed name accurately and provide it to the storage administrator when the host must be identified or authorized.

A software iSCSI adapter implements iSCSI connectivity through ESXi software. Make sure the selected adapter is the intended software adapter, especially when the host has multiple storage adapters.

Practical Configuration Example

Suppose a storage team asks for the initiator identifier of an ESXi host before configuring access to a new iSCSI datastore. Select the host, open its storage adapter list, select the software iSCSI adapter, and copy the displayed iSCSI name from the adapter status details. Provide that name rather than an IP address alone.

The storage team can then use the identifier in target-side access control. The IP address and networking details are still needed to establish connectivity, but the iSCSI name identifies which initiator is being granted access.

Troubleshooting Naming Problems

The Storage Administrator Cannot Identify the ESXi Host

  • Open the selected host's storage adapter details in the vSphere Web Client.
  • Confirm that the selected adapter is the intended software iSCSI adapter.
  • Provide the iSCSI name shown in the adapter status information.
  • Do not rely on an IP address as the sole host identifier.

An Initiator or Target Name Is Rejected

  • Determine whether the implementation expects IQN or EUI syntax.
  • For an IQN, check the iqn prefix, date, reverse-domain naming authority, colon separator, and unique-name portion.
  • For an EUI, check the eui prefix and confirm that exactly 16 hexadecimal digits follow it.
  • Look for transcription errors, omitted characters, invalid hexadecimal characters, or misplaced punctuation.

Two Nodes Appear to Have the Same Identifier

  • Treat duplicate node names as an identity conflict.
  • Review the unique-name portion of each IQN or the organization-assigned portion of each EUI.
  • Ensure that every initiator and target has a distinct configured identifier.
  • Correct the naming conflict before relying on target-side access controls.

Exam- and Operations-Relevant Notes

  • An iSCSI node is either an initiator or a target.
  • An iSCSI name is independent of the node's IP address.
  • IQNs use the structure iqn.yyyy-mm.naming-authority:unique-name.
  • The IQN date identifies when the naming authority was established.
  • EUIs use the eui prefix and exactly 16 hexadecimal digits representing 64 bits.
  • The first 24 EUI bits identify the IEEE-assigned company identifier, and the final 40 bits are assigned by that organization.
  • When configuring access, use the exact iSCSI name displayed for the intended ESXi adapter.

Related ESXi Storage Topics

For broader administration context, see the VMware ESXi online course, and review access control systems when connecting node identity with authorization.