Dell POWEREDGE M1000E - Manual (Page 282)

282 Managing General System Settings
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.
What Configuration Is Required for Plug-In Modules?
The switch supports several different plug-in modules (also known as cards)
for the expansion slots located on the back of the switch. For information
about the slots and the supported modules, see "PowerConnect M6220,
M6348, M8024, and M8024-k Front Panel" on page 83. You can preconfigure
the card type prior to inserting it into the switch.
Hot-swap support is available for plug-in modules, which means the switch
does not require a reboot when you insert or remove cards. However, the
switch does require a reboot to change the role of the ports on a CX-4 module
from stacking to Ethernet or vice-versa. The CX-4 modules will operate in the
mode for which they are configured. All other plug-in modules will default to
Ethernet mode upon rebooting the switch.
Before inserting a new module into the expansion slot, issue a no slot or clear
config command from the CLI so that the switch can recognize the new
module.