Cisco ASA 5505 Configuration Manual page 273

Chapter 9 Configuring Basic Settings
Setting the Date and Time Using an NTP Server
To obtain the date and time from an NTP server, perform the following steps.
Detailed Steps
The Configuration > Device Setup > System Time > NTP NTP pane lets you define NTP servers to
dynamically set the time on the adaptive security appliance. The time displays in the status bar at the
bottom of the main ASDM pane.
Time derived from an NTP server overrides any time set manually in the Clock pane.
NTP is used to implement a hierarchical system of servers that provide a precisely synchronized time
among network systems. This kind of accuracy is required for time-sensitive operations, such as
validating CRLs, which include a precise time stamp. You can configure multiple NTP servers. The
adaptive security appliance chooses the server with the lowest stratum—a measure of how reliable the
data is.
Fields
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Add/Edit NTP Server Configuration
The Configuration > Device Setup > System Time > NTP > Add/Edit NTP Server Configuration dialog
box lets you add or edit an NTP server.
Fields
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OL-20339-01
NTP Server List—Shows defined NTP servers.
IP Address—Shows the NTP server IP address.
–
Interface—Specifies the outgoing interface for NTP packets, if configured. The system does not
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include any interfaces, so it uses the admin context interfaces. If the interface is blank, then the
adaptive security appliance uses the default admin context interface according to the routing
table.
– Preferred?—Shows whether this NTP server is a preferred server, Yes or No. NTP uses an
algorithm to determine which server is the most accurate and synchronizes to that one. If servers
are of similar accuracy, then the preferred server is used. However, if a server is significantly
more accurate than the preferred one, the adaptive security appliance uses the more accurate
one. For example, the adaptive security appliance uses a more accurate server over a less
accurate server that is preferred.
Key Number—Shows the authentication key ID number.
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Trusted Key?—Shows if the key is a trusted key, Yes or No. The key must be trusted for
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authentication to work.
Enable NTP Authentication—Enables authentication for all servers.
Add—Adds an NTP server.
Edit—Edits an NTP server.
Delete—Deletes and NTP server.
IP Address—Sets the NTP server IP address.
Cisco ASA 5500 Series Configuration Guide using ASDM
Setting the Date and Time
9-3