• NTP can operate in authenticate or non-authenticate mode. Only symmetric key authentication is
supported.
• By default, NTP operates in default VLAN and it can be changed.
Limitations
• FastIron devices cannot operate as primary time server (or stratum 1). It only serves as secondary
time server (stratum 2 to 15).
• NTP server and client cannot communicate using hostnames.
• NTP is not supported on VRF enabled interface.
• Autokey public key authentication is not supported.
• The NTP version 4 Extension fields are not supported. The packets containing the extension fields
are discarded.
• The NTP packets having control (6) or private (7) packet mode is not supported. NTP packets with
control and private modes will be discarded.
• On reboot or switchover, all the NTP state information will be lost and time synchronization will start
fresh.
• NTP multicast server/client and manycast functionalities are not supported.
• NTP versions 1 and 2 are not supported.
• NTP MIB is not supported.
Network Time Protocol (NTP) leap second
A leap second is a second added to Coordinated Universal Time (UTC) in order to keep it synchronized
with astronomical time (UT1).
There are two main reasons that cause leap seconds to occur. The first is that the atomic second
defined by comparing cesium clocks to the Ephemeris Time (ET) scale was incorrect, as the duration of
the ephemeris second was slightly shorter than the mean solar second and this characteristic was
passed along to the atomic second. The second reason for leap seconds is that the speed of the Earth's
rotation is not constant. It sometimes speeds up, and sometimes slows down, but when averaged over
long intervals the trend indicates that it is gradually slowing. This gradual decrease in the rotational rate
is causing the duration of the mean solar second to gradually increase with respect to the atomic
second.
Leap seconds are added in order to keep the difference between UTC and astronomical time (UT1) to
less than 0.9 seconds. The International Earth Rotation and Reference Systems Service (IERS),
measures Earth's rotation and publishes the difference between UT1 and UTC. Usually leap seconds
are added when UTC is ahead of UT1 by 0.4 seconds or more.
How Brocade supports leap second handling for NTP
The obvious question raised is what happens during the NTP leap second itself.
Specifically, a positive leap second is inserted between second 23:59:59 of a chosen UTC calendar
date (the last day of a month, usually June 30 or December 31) and second 00:00:00 of the following
date. This extra second is displayed on UTC clocks as 23:59:60. On clocks that display local time tied to
UTC, the leap second may be inserted at the end of some other hour (or half-hour or quarter-hour),
depending on the local time zone. When ever there is a leap second the NTP server notifies by setting
the NTP leap second bits.
On Brocade devices when ever there is a negative leap second, the clock is set once second backward
of the following date as described here. On positive leap second the clock suppress second 23:59:59 of
Limitations
FastIron Ethernet Switch Administration Guide
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