Configure NTP time server synchronisation on Cisco routers
Maybe you want an accurate time source on your internal network for your servers to sync against. Or maybe you just want your Cisco box to report the correct time! In either case – you’ll need NTP.
First, we’ll sync the router time against another NTP time source. It’s as easy as specifying an IP:
phbrtr#conf t
Enter configuration commands, one per line. End with CNTL/Z.
phbrtr(config)#ntp server <IP address>
phbrtr(config)#exit
phbrtr#
Incidentally, you can find a list of public NTP servers at:
To tidy things up, you might want to prevent NTP synchronisation attempts on a per-interface basic. To do this, you can ‘ntp disable’ on the relevant interface(s):
phbrtr#conf t
Enter configuration commands, one per line. End with CNTL/Z.
phbrtr(config)#interface fa1/0
phbrtr(config-if)#ntp disable
phbrtr(config-if)#exit
phbrtr(config)#exit
Finally, heres how to check that everything’s working as it should:
phbrtr#sh ntp status
Clock is synchronized, stratum 2, reference is 129.6.15.28
nominal freq is 250.0000 Hz, actual freq is 250.0005 Hz, precision is 2**24
reference time is CE89F9F3.27B5E326 (21:21:55.155 GMT Wed Oct 21 2009)
clock offset is -13.4327 msec, root delay is 99.40 msec
root dispersion is 21.27 msec, peer dispersion is 7.83 msec
phbrtr#
Are you looking to learn more about Cisco equipment? Well, here’s a selection of a few books that I’ve found useful over the years:
 Cisco: A Beginner’s Guide |
 CCNA – Cisco Certified Network Associate Study Guide |
 Cisco Networking for Dummies |
 Cisco IOS in a Nutshell – O’Reilly |
