System Time Window
This window appears when you choose Administration > System Time on
the menu bar. You can also click here
to launch it.
Use this window to:
The Set Current Time tab of the System Time Management window automatically
displays the current time: hours (in 24-hour format), minutes, seconds, milliseconds,
time zone, weekday name, month, day, date, and year.
Generally, you do not need to set the system clock if the system is synchronized by a
valid outside timing mechanism such as NTP. If no other time source is available, you
should manually set the time. The time specified is relative to the configured time zone.
To manually set the system time:
- Click the Set Current Time tab.
- In the Set System Time Manually section, select the correct month,
day, and year from the drop-down lists.
- Select the correct hour, minutes, and seconds from the drop-down lists.
Your hour selection must be based on 24-hour format. For example, for 9 A.M.,
enter 09; for 1 P.M., enter 13; for midnight,
enter 24.
- In the UTC Offset section, select the hours offset from the Hours
Offset from UTC list.
Universal Time Coordinated (UTC) is the same as Greenwich Mean Time. The offset
(difference between UTC and the time zone of the switch) can be a negative
or positive number. For example, Pacific Standard Time has an offset of -8
hours, meaning it is 8 hours behind UTC.
- Select the minutes offset from the Minutes Offset from UTC list.
Note: If hours are negative, minutes are assumed to be negative.
- In the Name of the Time Zone field, enter the name of the zone to
be displayed when standard time is in effect.
For example, enter PST for Pacific Standard Time.
- Click Apply to put your changes on this tab in effect.
The values that you selected are propagated to all the members of the cluster.
- Configure daylight saving
time if it is applicable to your area.
- Click OK to close the System Time Management window.
The Set Daylight Saving Time tab configures summer time or daylight
saving time for three conditions:
- Daylight saving time does not apply to your area.
- Daylight saving time starts and ends on a particular day of the week each year
(recurring pattern).
- Daylight saving time starts and ends on an exact date and time.
By default, the switch does not adjust for daylight saving time. To configure
daylight saving time:
- In the Name of the Summer Time Zone field, enter the name of the
time zone to be displayed when summer or daylight time is in effect.
For example, enter PDT for Pacific Daylight Time.
- From the Minutes to Add During Summer Time list, select the
number of minutes to set the clock forward for summer or daylight time.
The default is 60 minutes.
- Use Configuring for a Recurring
Summer Event or Configuring for an
Exact Date and Time to complete the configuration.
If your daylight saving time occurs on a particular day of the week each year in a
recurring pattern:
- Click Use Day above the Start section.
- From the drop-down lists in the Start section, select the week and
day that the time change begins.
- Select the hour and minutes that the time change begins.
- From the drop-down lists in the End section, select the week and
day that the time change ends.
- Select the hour and minute that the time change ends.
- Click Apply to put your changes on this tab in effect.
- Click OK to close the System Time Management window.
If your daylight saving time starts and ends on an exact date and time:
- Click Use Date above the Start section.
- From the drop-down lists in the Start section, select the month,
date, and year that the time change begins.
- Select the hour and minutes that the time change begins.
- From the drop-down lists in the End section, select the month, date,
and year that the time change ends.
- Select the hour and minute that the time change ends.
- Click Apply to put your changes on this tab in effect.
- Click OK to close the System Time Management window.
Configure the switch as an NTP client if you want it to regularly send time-of-day
requests to an NTP server (or see Configuring the Switch as an NTP
Broadcast Client). The NTP server then synchronizes the client system clock to the
clock on the server when the switch requests it. To enhance security, you can configure
NTP authentication (see Configuring NTP
Authentication).
To configure your switch to receive time updates from an NTP server:
- Click the Network Time Protocol tab.
- In the IP Address field of the NTP Server section, enter the
IP address of the time server.
You can configure up to 10 server addresses per client.
- Optional: In the Ver (version) field, enter the NTP version
number.
You can enter a number from 1 to 3; the default is version 3.
Note: If you are using the default version (3) and NTP synchronization
does not occur, try using NTP version 2. Many NTP servers on the Internet run version 2.
- Optional: In the Key ID field, enter the authentication key
to use when sending packets to the server (if authentication is enabled).
Enter a number from 0 to 4294967295. The default is 0, which means that authentication is
not in effect. If authentication is disabled, the system clock on the client switch is
updated.
- Optional: Check the Preferred Server box if you
want this server to be the preferred server for synchronization.
Selecting a preferred server reduces the switching back and forth among servers if
multiple NTP servers are configured.
- Click Add to add the server address to the list.
(To remove an NTP server address from this list, select the address from the
list and click Remove.)
- Repeat this procedure to add more NTP servers.
- Click Apply to put your changes on this tab in effect.
- Click OK to close the System Time Management window.
Authentication enhances the security of a system running the NTP protocol. When NTP
authentication is set, the switch updates the time only from servers that provide the
correct authentication. By default, NTP authentication is disabled.
The authentication scheme designed for NTP uses the public-key cryptography
with the Message Digest (MD5) algorithm. With this scheme, every message must
be individually signed by using an authentication key. The key consists of two
parts: a public key number (a 32-bit integer) and a secret key value (an arbitrary
string of up to 32 characters). To authenticate a message, the client must have
the authentication key (public/secret key pair) matched with the one on the
server. Therefore, the authentication key must be securely distributed in advance;
the client administrator must obtain the key pair from the server administrator
and configure it on the client. The public key is known as the key identifier
and key number. The secret key is known as the key value.
Note: For authentication to work properly, you must obtain the key
information from the server administrator in advance and enter it in the NTP
Authentication field.
To enable authentication:
- Deselect Authentication Disabled above the NTP Authentication
section.
- In the Key Number field of the NTP Authentication section,
enter a public key number.
Enter a number from 1 to 4294967295.
- In the Key Value field, enter the secret key.
Enter up to 32 printable characters, including alphanumeric keys, spaces,
and !, ", #, $, }, |, and ~. No control or escape characters are allowed.
Note: The switch can store a maximum of ten authentication
keys at a time.
- Optional: In the Encryption Type field, enter the number used
to encrypt the key value.
Enter a number from 0 to 4294967295.
- Optional: Check the Trusted box if you want the
authentication key to be trusted.
This setting defines one or more key numbers that an NTP server must provide in its
packets for the client system to synchronize its clock to the server clock. A trusted
server provides protection against accidentally synchronizing the client clock to a system
that does not have the correct authentication key.
- Click Add to add the key to the list.
- Repeat this procedure to add more authentication keys.
- Click Apply to put your changes on this tab in effect.
- Click OK to close the System Time Management window.
To remove authentication information, select it in the list box and click Remove.
Configure the switch as an NTP broadcast client if an NTP broadcast server, such as a
router, regularly broadcasts time-of-day information over the network (also see Configuring the Switch as an NTP Client).
To compensate for any server-to-client packet latency, you can specify an estimated NTP
broadcast delay (a time adjustment factor for receiving broadcast packets from the
server). By default, the NTP broadcast client is disabled on the switch.
To configure your switch to receive NTP broadcast packets on an interface:
- Check the Received NTP Broadcast Client box.
- Optional: In the Estimated Round-Trip Delay field, enter a
number from 1 to 999999 (microseconds).
The default is 3000 microseconds. This number is the estimated round-trip delay between
the client and the NTP broadcast server.
- Click Apply to put your changes on this tab in effect.
- Click OK to close the System Time Management window.