KB.15.15

1 Time Protocols

General steps for running a time protocol on the switch

Using time synchronization ensures a uniform time among interoperating devices. This helps you

to manage and troubleshoot switch operation by attaching meaningful time data to event and error

messages.

The switch offers TimeP and SNTP (Simple Network Time Protocol) and a timesync command

for changing the time protocol selection (or turning off time protocol operation.)

NOTE: Although you can create and save configurations for both time protocols without conflicts,

the switch allows only one active time protocol at any time.

In the factory-default configuration, the time synchronization option is set to TimeP, with the TimeP

mode itself set to Disabled.

1. Select a time synchronization protocol: SNTP or TimeP (the default.)

2. Enable the protocol; the choices are:

• SNTP: Broadcast or Unicast

• TimeP: DHCP or Manual

3. Configure the remaining parameters for the time protocol you selected.

NOTE: The switch retains the parameter settings for both time protocols even if you change

from one protocol to the other. Thus, if you select a time protocol, the switch uses the parameters

you last configured for the selected protocol.

4. View the configuration.

IMPORTANT: Simply selecting a time synchronization protocol does not enable that protocol on

the switch unless you also enable the protocol itself (step 2, above.) For example, in the

factory-default configuration, TimeP is the selected time synchronization method. However, because

TimeP is disabled in the factory-default configuration, no time synchronization protocol is running.

About SNTP time synchronization

SNTP provides two operating modes:

• Broadcast mode

The switch acquires time updates by accepting the time value from the first SNTP time broadcast

detected. (In this case, the SNTP server must be configured to broadcast time updates to the

network broadcast address; see the documentation provided with your SNTP server application.)

Once the switch detects a particular server, it ignores time broadcasts from other SNTP servers

unless the configurable Poll Interval expires three consecutive times without an update received

from the first-detected server. If the Poll Interval (configurable up to 720 seconds) expires three

times without the switch detecting a time update from the original server, the switch accepts

a broadcast time update from the next server it detects.

NOTE: To use Broadcast mode, the switch and the SNTP server must be in the same subnet.

• Unicast mode

The switch periodically requests a time update, for the purposes of time synchronization, from

the configured SNTP server. (You can configure one server using the menu interface, or up to

three servers using the CLI sntp server command.) This option provides increased security

over the Broadcast mode by specifying which time server to use instead of using the first one

22 Time Protocols