Configuring Ntp Broadcast Service - Cisco WS-C3560-48PS-S Software Configuration Manual

Chapter 6 Administering the Switch

Configuring NTP Broadcast Service

The communications between devices running NTP (known as associations) are usually statically
configured; each device is given the IP addresses of all devices with which it should form associations.
Accurate timekeeping is possible by exchanging NTP messages between each pair of devices with an
association. However, in a LAN environment, NTP can be configured to use IP broadcast messages
instead. This alternative reduces configuration complexity because each device can simply be configured
to send or receive broadcast messages. However, the information flow is one-way only.
The switch can send or receive NTP broadcast packets on an interface-by-interface basis if there is an NTP
broadcast server, such as a router, broadcasting time information on the network. The switch can send NTP
broadcast packets to a peer so that the peer can synchronize to it. The switch can also receive NTP broadcast
packets to synchronize its own clock. This section provides procedures for both sending and receiving NTP
broadcast packets.
Beginning in privileged EXEC mode, follow these steps to configure the switch to send NTP broadcast
packets to peers so that they can synchronize their clock to the switch:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3 ntp broadcast [version number] [key keyid]
[destination-address]
Step 4
end
Step 5
show running-config
Step 6
copy running-config startup-config
Step 7
To disable the interface from sending NTP broadcast packets, use the no ntp broadcast interface
configuration command.
This example shows how to configure a port to send NTP version 2 packets:
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# ntp broadcast version 2
78-16156-01
Purpose
Enter global configuration mode.
Specify the interface to send NTP broadcast packets, and enter
interface configuration mode.
Enable the interface to send NTP broadcast packets to a peer.
By default, this feature is disabled on all interfaces.
(Optional) For number, specify the NTP version number. The
•
range is 1 to 3. If you do not specify a version, version 3 is used.
• (Optional) For keyid, specify the authentication key to use when
sending packets to the peer.
(Optional) For destination-address, specify the IP address of the
•
peer that is synchronizing its clock to this switch.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Configure the connected peers to receive NTP broadcast packets as
described in the next procedure.
Catalyst 3560 Switch Software Configuration Guide
Managing the System Time and Date
6-7