iSCSI storage systems authenticate an initiator using a name and key pair. ESXi systems support Challenge Handshake Authentication Protocol (CHAP).
Using CHAP for your SAN implementation is a best practice. The ESXi host and the iSCSI storage system must have CHAP enabled and must have common credentials. During iSCSI login, the iSCSI storage system exchanges its credentials with the ESXi system and checks them.
You can set up iSCSI authentication by using the vSphere Client, as discussed in the vSphere Storage documentation or by using the esxcli command, discussed in Enabling iSCSI Authentication. To use CHAP authentication, you must enable CHAP on both the initiator side and the storage system side. After authentication is enabled, it applies for targets to which no connection has been established, but does not apply to targets to which a connection is established. After the discovery address is set, the new volumes to which you add a connection are exposed and can be used.
For software iSCSI and dependent hardware iSCSI, ESXi hosts support per-discovery and per-target CHAP credentials. For independent hardware iSCSI, ESXi hosts support only one set of CHAP credentials per initiator. You cannot assign different CHAP credentials for different targets.
When you configure independent hardware iSCSI initiators, ensure that the CHAP configuration matches your iSCSI storage. If CHAP is enabled on the storage array, it must be enabled on the initiator. If CHAP is enabled, you must set up the CHAP authentication credentials on the ESXi host to match the credentials on the iSCSI storage.
Supported CHAP Levels
To set CHAP levels with esxcli iscsi adapter setauth, specify one of the values in Supported Levels for CHAP for <level>. Only two levels are supported for independent hardware iSCSI.
Mutual CHAP is supported for software iSCSI and for dependent hardware iSCSI, but not for independent hardware iSCSI.
chapRequired before you set mutual CHAP, and use compatible levels for CHAP and mutual CHAP. Use different passwords for CHAP and mutual CHAP to avoid security risks.
| Level | Description | Supported |
|---|---|---|
chapProhibited |
Host does not use CHAP authentication. If authentication is enabled, specify chapProhibited to disable it. |
Software iSCSI Dependent hardware iSCSI Independent hardware iSCSI |
chapDiscouraged |
Host uses a non-CHAP connection, but allows a CHAP connection as fallback. | Software iSCSI Dependent hardware iSCSI |
chapPreferred |
Host uses CHAP if the CHAP connection succeeds, but uses non-CHAP connections as fallback. | Software iSCSI Dependent hardware iSCSI Independent hardware iSCSI |
chapRequired |
Host requires successful CHAP authentication. The connection fails if CHAP negotiation fails. | Software iSCSI Dependent hardware iSCSI |
Returning Authentication to Default Inheritance
The values of iSCSI authentication settings associated with a dynamic discovery address or a static discovery target are inherited from the corresponding settings of the parent. For the dynamic discovery address, the parent is the adapter. For the static target, the parent is the adapter or discovery address.
- If you use the vSphere Client to modify authentication settings, you must deselect the Inherit from Parent check box before you can make a change to the discovery address or discovery target.
- If you use esxcli iscsi commands, the value you set overrides the inherited value. You can set CHAP at the following levels.
-
esxcli iscsi adapter auth chap [get|set]
-
esxcli iscsi adapter discovery sendtarget auth chap [get|set]
-
esxcli iscsi adapter target portal auth chap [get|set]
-
Inheritance is relevant only if you want to return a dynamic discovery address or a static discovery target to its inherited value. In that case, use one of the following commands.
- Dynamic discovery
esxcli iscsi adapter discovery sendtarget auth chap set --inherit
- Static discovery
esxcli iscsi adapter target portal auth chap set --inherit
