Using NTP to Send Periodic Broadcast Time Updates
Problem
You want to set up your router to use the NTP broadcast mode so that devices do not need to query periodically for the time.
Solution
Use the NTP broadcast interface configuration command to enable server-side NTP broadcasts:
Router1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z. Router1(config)#clock timezone
EST -5 Router1(config)#clock summer-time
EDTrecurring
Router1(config)#ntp server
172.25.1.1 Router1(config)#ntp server
172.25.1.2 Router1(config)#interface
FastEthernet0/0 Router1(config-if)#ntp broadcast
Router1(config-if)#end
Router1#
To enable a NTP broadcast client on the router, enter the following:
Router2#configure terminal
Enter configuration commands, one per line. End with CNTL/Z. Router2(config)#clock timezone
Router2(config)#
EST -5
clock summer-time
EDT
recurring
Router2(config)#ntp broadcastdelay
Router2(config)#
4
interface
Router2(config-if)#
Ethernet0
ntp broadcast client
Router2(config-if)#end
Router2#
Discussion
Usually NTP associations are configured in a master/slave relationship, but the server (router) can also send periodic time updates using broadcast messages. This is useful on LAN segments that contain a large number of devices requiring NTP synchronization. Instead of responding to a large number of unicast NTP packets through a single interface, the router can simply send a single broadcast packet at a regular interval.
NTP devices configured to accept NTP broadcast ...
Get Cisco IOS Cookbook, 2nd Edition now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.