242 Managing General System Settings
Why is the System Time Needed?
The switch uses the system clock to provide time stamps on log messages.
Additionally, some show commands include the time in the command
output. For example, the show users login-history command includes a Login
Time field. The system clock provides the information for the Login Time
field.
How Does SNTP Work?
SNTP assures accurate switch clock time synchronization. Time
synchronization is performed by a network SNTP server.
Time sources are established by Stratums. Stratums define the accuracy of
the reference clock. The higher the stratum (where zero is the highest), the
more accurate the clock. The switch is at a stratum that is one lower than its
time source. For example, if the SNTP server in an internal network is a
Stratum 3 device, the switch is a Stratum 4 device.
You can configure the switch to request the time from an SNTP server on the
network, or you can allow the switch to receive SNTP broadcasts.
Requesting the time from a unicast SNTP server is more secure. Use this
method if you know the IP address of the SNTP server on your network. If you
allow the switch to receive SNTP broadcasts, any clock synchronization
information is accepted, even if it has not been requested by the device. This
method is less secure than polling a specified SNTP server.
To increase security, you can require authentication between the configured
SNTP server and the SNTP client on the switch. Authentication is provided
by Message Digest 5 (MD5). MD5 verifies the integrity of the
communication and authenticates the origin of the communication.
Default General System Information
By default, no system information or time information is configured, and the
SNTP client is disabled. The default SDM Template applied to the switch is
the Dual IPv4-IPv6 template.
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