
In LDAP, authorization can occur before authentication.
Note
LDAP Server Monitoring
An unresponsive LDAP server can delay the processing of AAA requests. A Cisco NX-OS device can
periodically monitor an LDAP server to check whether it is responding (or alive) to save time in processing
AAA requests. The Cisco NX-OS device marks unresponsive LDAP servers as dead and does not send AAA
requests to any dead LDAP servers. A Cisco NX-OS device periodically monitors dead LDAP servers and
brings them to the alive state once they are responding. This process verifies that an LDAP server is in a
working state before real AAA requests are sent its way. Whenever an LDAP server changes to the dead or
alive state, a Simple Network Management Protocol (SNMP) trap is generated, and the Cisco NX-OS device
displays an error message that a failure is taking place before it can impact performance. The following figure
shows the server states for LDAP server monitoring.
Figure 4: LDAP Server States
The monitoring interval for alive servers and dead servers is different and can be configured by the user. The
LDAP server monitoring is performed by sending a test authentication request to the LDAP server.
Note
Vendor-Specific Attributes for LDAP
The Internet Engineering Task Force (IETF) draft standard specifies a method for communicating
vendor-specific attributes (VSAs) between the network access server and the LDAP server. The IETF uses
attribute 26. VSAs allow vendors to support their own extended attributes that are not suitable for general
use.
Cisco VSA Format for LDAP
The Cisco LDAP implementation supports one vendor-specific option using the format recommended in the
IETF specification. The Cisco vendor ID is 9, and the supported option is vendor type 1, which is named
cisco-av-pair. The value is a string with the following format:
protocol : attribute separator value *
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Configuring LDAP
LDAP Server Monitoring