Configuring Ntp Access Restrictions - Cisco Catalyst 3550 series Software Configuration Manual

Chapter 7 Administering the Switch
Command
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 an interface to send NTP version 2 packets:
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# ntp broadcast version 2
Beginning in privileged EXEC mode, follow these steps to configure the switch to receive NTP broadcast
packets from connected peers:
Command
Step 1 configure terminal
Step 2
interface interface-id
Step 3
ntp broadcast client
Step 4 exit
Step 5 ntp broadcastdelay microseconds
Step 6
end
Step 7
show running-config
Step 8 copy running-config startup-config
To disable an interface from receiving NTP broadcast packets, use the no ntp broadcast client interface
configuration command. To change the estimated round-trip delay to the default, use the no ntp
broadcastdelay global configuration command.
This example shows how to configure an interface to receive NTP broadcast packets:
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# ntp broadcast client

Configuring NTP Access Restrictions

You can control NTP access on two levels as described in these sections:
•
•
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Purpose
Enter global configuration mode.
Specify the interface to receive NTP broadcast packets, and enter interface
configuration mode.
Enable the interface to receive NTP broadcast packets.
By default, no interfaces receive NTP broadcast packets.
Return to global configuration mode.
(Optional) Change the estimated round-trip delay between the switch and
the NTP broadcast server.
The default is 3000 microseconds; the range is 1 to 999999.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Creating an Access Group and Assigning a Basic IP Access List, page 7-8
Disabling NTP Services on a Specific Interface, page 7-9
Purpose
(Optional) Save your entries in the configuration file.
Configure the connected peers to receive NTP broadcast packets as
described in the next procedure.
Catalyst 3550 Multilayer Switch Software Configuration Guide
Managing the System Time and Date
7-7