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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 6 Administering the Switch
Managing the System Time and Date
To disable NTP authentication, use the no ntp authenticate global configuration command. To remove
an authentication key, use the no ntp authentication-key number global configuration command. To
disable authentication of the identity of a device, use the no ntp trusted-key key-number global
configuration command.
This example shows how to configure the switch to synchronize only to devices providing authentication
key 42 in the device’s NTP packets:
Switch(config)# ntp authenticate
Switch(config)# ntp authentication-key 42 md5 aNiceKey
Switch(config)# ntp trusted-key 42
Configuring NTP Associations
An NTP association can be a peer association (this switch can either synchronize to the other device or
allow the other device to synchronize to it), or it can be a server association (meaning that only this
switch synchronizes to the other device, and not the other way around).
Beginning in privileged EXEC mode, follow these steps to form an NTP association with another device:
Step 5
end
Return to privileged EXEC mode.
Step 6
show running-config
Verify your entries.
Step 7
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Command
Purpose
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ntp peer ip-address [version number]
[key keyid] [source interface] [prefer]
or
ntp server ip-address [version number]
[key keyid] [source interface] [prefer]
Configure the switch system clock to synchronize a peer or to be
synchronized by a peer (peer association).
or
Configure the switch system clock to be synchronized by a time server
(server association).
No peer or server associations are defined by default.
•
For ip-address in a peer association, specify either the IP address of
the peer providing, or being provided, the clock synchronization. For
a server association, specify the IP address of the time server
providing the clock synchronization.
•
(Optional) For number, specify the NTP version number. The range is
1 to 3. By default, version 3 is selected.
•
(Optional) For keyid, enter the authentication key defined with the
ntp authentication-key global configuration command.
•
(Optional) For interface, specify the interface from which to pick the
IP source address. By default, the source IP address is taken from the
outgoing interface.
•
(Optional) Enter the prefer keyword to make this peer or server the
preferred one that provides synchronization. This keyword reduces
switching back and forth between peers and servers.
