6.5.1

Table Of Contents
ESXi supports CHAP authentication at the adapter level. In this case, all targets receive the same CHAP
name and secret from the iSCSI initiator. For software and dependent hardware iSCSI adapters, ESXi
also supports per-target CHAP authentication, which allows you to configure different credentials for each
target to achieve greater level of security.
Selecting CHAP Authentication Method
ESXi supports unidirectional CHAP for all types of iSCSI initiators, and bidirectional CHAP for software
and dependent hardware iSCSI.
Before configuring CHAP, check whether CHAP is enabled at the iSCSI storage system. Also, obtain
information about the CHAP authentication method the system supports. If CHAP is enabled, configure it
for your initiators, making sure that the CHAP authentication credentials match the credentials on the
iSCSI storage.
ESXi supports the following CHAP authentication methods:
Unidirectional CHAP In unidirectional CHAP authentication, the target authenticates the initiator,
but the initiator does not authenticate the target.
Bidirectional CHAP The bidirectional CHAP authentication adds an extra level of security. With
this method, the initiator can also authenticate the target. VMware supports
this method for software and dependent hardware iSCSI adapters only.
For software and dependent hardware iSCSI adapters, you can set unidirectional CHAP and bidirectional
CHAP for each adapter or at the target level. Independent hardware iSCSI supports CHAP only at the
adapter level.
When you set the CHAP parameters, specify a security level for CHAP.
Note When you specify the CHAP security level, how the storage array responds depends on the array’s
CHAP implementation and is vendor-specific. For information on CHAP authentication behavior in
different initiator and target configurations, consult the array documentation.
Table 114. CHAP Security Level
CHAP Security Level Description Supported
None The host does not use CHAP authentication. If
authentication is enabled, use this option to disable it.
Software iSCSI
Dependent hardware iSCSI
Independent hardware iSCSI
Use unidirectional CHAP if
required by target
The host prefers a non-CHAP connection, but can use a
CHAP connection if required by the target.
Software iSCSI
Dependent hardware iSCSI
Use unidirectional CHAP unless
prohibited by target
The host prefers CHAP, but can use non-CHAP connections
if the target does not support CHAP.
Software iSCSI
Dependent hardware iSCSI
Independent hardware iSCSI
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