Configuring Ntp Access Restrictions - Cisco Catalyst 3750-X Software Configuration Manual

Managing the System Time and Date
Command
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 a port to receive NTP broadcast packets:
Switch(config)# interface gigabitethernet1/0/1
Switch(config-if)# ntp broadcast client

Configuring NTP Access Restrictions

You can control NTP access on two levels as described in these sections:
•
•
Creating an Access Group and Assigning a Basic IP Access List
Beginning in privileged EXEC mode, follow these steps to control access to NTP services by using
access lists:
Command
Step 1
configure terminal
ntp access-group {query-only |
Step 2
serve-only | serve | peer}
access-list-number
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
7-8
Purpose
(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 7-10
Purpose
Enter global configuration mode.
Create an access group, and apply a basic IP access list.
The keywords have these meanings:
For access-list-number, enter a standard IP access list number from 1
to 99.
query-only—Allows only NTP control queries.
•
serve-only—Allows only time requests.
•
serve—Allows time requests and NTP control queries, but does not
•
allow the switch to synchronize to the remote device.
peer—Allows time requests and NTP control queries and allows the
•
switch to synchronize to the remote device.
Chapter 7 Administering the Switch
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