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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 7 Administering the Switch
Managing the Syste m Ti m e and Date
To disable NT P authent ication, use the no ntp authenticate global configuration command. To remove
an authentication key, use the no ntp authentication-key number gl ob al co nfigurat ion c omm and. To
disable authentication of the identity of a device, use the no ntp trusted-key key-number globa l
configurati on comm a nd.
This e xample sho ws how to configur e the switch to synch ronize only to de vices pro viding authenticati on
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 associat ion can be a pe er asso cia tio n (this swi tch ca n eit her sync hroni ze to th e othe r device or
allow the other device to sync hronize to it), or it ca n be a server associati on (meani ng that on ly this
switch synchr onize s 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 de vice:
Step 5 end Return to pr ivileged EX EC m ode.
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 globa l configurati on 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 swit ch sy st em c loc k to be s ync hro niz ed by a t ime se rver
(server associa tion).
No peer or server asso ciatio ns 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 c lock synch roniza tion.
•(Optional) For number, specify the NTP version number . The range is
1 to 3. By d efaul t, vers ion 3 i s sele cte d.
•(Optiona l) For keyid, enter the authentication key defined with the
ntp au the nti cati on- key g loba l c onfigura tion c om mand.
•(Optional) For interface, specif y the interf ace f rom which to pick th e
IP sour ce add res s. By def au lt, the so urce IP addr ess is tak en fr om the
outgoing in terface.
•(Optional) Enter the prefer keyword to make this pe er or server the
preferred on e tha t pr ovides sy nc hroni zat ion. Thi s keyword reduc es
switching bac k and fo rth be twee n pee rs and servers.