How to setup NTP on Cisco router with summer-time zone

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Accurate clock record is very information when you are troubling an issue. In these days, many NTP servers are availabe to use as free. However, you might want to pick good one which is lower stratum. Lower stratum number(1~3) is better. I will intend to make simple list of NTP servers based on each region. Currently, I am on east zone of USA and In this below example, I will use 128.249.1.1 which is stratum 3.

 

Cisco_Router#
Cisco_Router(config)#ntp server 128.249.1.1

 

Done, you might need to wait to synchronize your Cisco router to NTP server. It take few minutes. Be patient!

You can check with below command(below), it will give you NTP status

Cisco_Router#show ntp status
Clock is synchronized, stratum 3, reference is 128.249.1.1
nominal freq is 250.0000 Hz, actual freq is 249.9981 Hz, precision is 2**18
reference time is CDB93371.D03D5B6B (08:43:29.813 EDT Sat May 16 2009)
clock offset is -4.7340 msec, root delay is 83.56 msec
root dispersion is 57.02 msec, peer dispersion is 15.29 msec
Cisco_Router#

Let’s add summer-time zone setup.

Cisco_Router(config)#clock timezone EST -5
Cisco_Router(config)#clock summer-time EDT date Apr 30 2008 0:00 Sep 30 2035 0:00

or

Cisco_Router(config)#clock summer-time EDT recurring 2 Sunday march 02:00 1 Sunday november 02:00
 

Now, check clock on your Cisco gear
 

Cisco_Router#show clock
08:55:50.517 EDT Sat May 16 2009
Cisco_Router#
 

 

Case study>> NTP redundancy.

– NTP source : 128.249.1.1
– Local : Eastern time zone.
– Two Cisco 6509 Core Layer switches : C6509A & B
– Ten Cisco 3750 Access Layer switches : C3750
– VRRP IP : 10.10.10.1

 

[common]

clock timezone EST -5 (If you are at Eastern timezone : NY)
clock summer-time EDT recurring 2 sunday march 02:00 1 sunday november 02:00
* Summer-time peirod Since 2007 – 2nd week on Sunday ~ 1st week on Sunday.
clock calendar-vaild(depend on IOS ver.)

 

[C6509A:10.10.10.2/24] – Prefer

ntp logging
ntp authentication-key 123 md5 xxxxx
ntp authenticate
ntp trusted-key 123
ntp source loopback 0
ntp master 5
ntp update-calendar
ntp peer 10.10.10.3 key 123 source VLAN xxx
ntp server 128.249.1.1 source vlan xxx prefer

 

[C6509B:10.10.10.3/24] – Backup

ntp logging
ntp authentication-key 123 md5 xxxxx
ntp authenticate
ntp trusted-key 123
ntp source loopback 0
ntp master 10
ntp update-calendar
ntp peer 10.10.10.2 key 123 source VLAN xxx
ntp server 128.249.1.1 source vlan xxx prefer

 

[C3750: 10.10.10.11/24] – Access Layer Switch

ntp logging
ntp authentication-key 123 md5 xxxxx
ntp authenticate
ntp trusted-key 123
ntp server 10.10.10.2 key 123 prefer
ntp server 10.10.10.3 key 123