Brocade FastIron Ethernet Switch Administration Guide - Manual (Page 41)

The NTP client maintains the server and peer state information as association. The server and peer
association is mobilized at the startup or whenever user configures. The statically configured server/
peer associations are not demobilized unless user removes the configuration. The symmetric passive
association is mobilized upon arrival of NTP packet from peer which is not statically configured. The
associations will be demobilized on error or time-out.
NTP peer
NTP peer mode is intended for configurations where a group of devices operate as mutual backups for
each other. If one of the devices loses a reference source, the time values can flow from the surviving
peers to all the others. Each device operates with one or more primary reference sources, such as a
radio clock, or a subset of reliable NTP secondary servers. When one of the devices lose all reference
sources or simply cease operation, the other peers automatically reconfigures so that time values can
flow from the surviving peers to others.
When the NTP server or peer is configured with burst mode, client will send burst of up to 8 NTP
packets in each polling interval. The burst number of packets in each interval increases as the polling
interval increases from minimum polling interval towards maximum interval.
The NTP peer can operate in:
• Symmetric Active-When the peer is configured using the peer command.
• Symmetric Passive-Dynamically learned upon arrival of a NTP packet from the peer which is not
configured. The symmetric passive association is removed on timeout or error.
The following scenarios are observed when the upstream server is not reachable after retries:
• If the NTP server/peer is configured and the master command is not configured, then the system
clock is synchronized. When the system clock is synchronized, the server will respond to client's
request with the stratum number set to +1. And when the system clock is unsynchronized, the server
will respond to client's request with the stratum number set to 16.
• If the NTP server/peer is configured and the master command is configured, then the system clock is
synchronized. When the system clock is synchronized, the reference time is the local clock time. If
the local clock is valid then the server will respond to client's request with the specified stratum
number if it is configured otherwise with the default stratum number.
The following scenarios are observed when you remove the last NTP server/peer under the conditions -
the NTP server/peer is configured, master command is not configured, system clock is synchronized
and the reference time is the NTP time:
• If the local clock is not valid, the system clock is not synchronized.
• If the local clock is valid, the system clock is synchronized and the reference time is the local clock.
The server will respond to the client's request with the specified stratum number if it is configured
otherwise with the default stratum number.
NOTE
To create a symmetric active association when a passive association is already formed, disable NTP,
configure peer association and then enable NTP again.
NTP broadcast server
An NTP server can also operate in a broadcast mode. Broadcast servers send periodic time updates to
a broadcast address, while multicast servers send periodic updates to a multicast address. Using
broadcast packets can greatly reduce the NTP traffic on a network, especially for a network with many
NTP clients.
The interfaces should be enabled with NTP broadcasting. The NTP broadcast server broadcasts the
NTP peer
FastIron Ethernet Switch Administration Guide 41
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