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Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 7 Administering the Switch
Managing the System Time and Date
Disabling NTP Services on a Specific Interface
NTP services are enabled on all interfaces by default.
Beginning in privileged EXEC mode, follow these steps to disable NTP packets from being received on
an interface:
To re-enable receipt of NTP packets on an interface, use the no ntp disable interface configuration
command.
Configuring the Source IP Address for NTP Packets
When the switch sends an NTP packet, the source IP address is normally set to the address of the
interface through which the NTP packet is sent. Use the ntp source global configuration command when
you want to use a particular source IP address for all NTP packets. The address is taken from the
specified interface. This command is useful if the address on an interface cannot be used as the
destination for reply packets.
Beginning in privileged EXEC mode, follow these steps to configure a specific interface from which the
IP source address is to be taken:
The specified interface is used for the source address for all packets sent to all destinations. If a source
address is to be used for a specific association, use the source keyword in the ntp peer or ntp server
global configuration command as described in the
“Configuring NTP Associations” section on page 7-5.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify the interface to disable.
Step 3
ntp disable Disable NTP packets from being received on the interface.
By default, all interfaces receive NTP packets.
Step 4
end Return to privileged EXEC mode.
Step 5
show running-config Verify your entries.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
ntp source type number Specify the interface type and number from which the IP source address
is taken.
By default, the source address is set by the outgoing interface.
Step 3
end Return to privileged EXEC mode.
Step 4
show running-config Verify your entries.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.