CDQ: NTP will save you time.

In my second edition of Cisco Done Quick (CDQ) I will talk about how NTP – the network time protocol – will save you time.

Debugging network problems can be challenging. It’s made even worse by time zones and daylight savings time.  Worse still by a clock that has drifted.

Some older Cisco IOSes don’t know the current rules for daylight savings. They can be configured, if necessary. Start with setting a timezone and setting the rules for Mountain Daylight Time (or your time zone as appropriate):

clock timezone MST -7 0
clock summer-time MDT recurring 2 sunday march 02:00 1 sunday november 02:00 60

Next, setup NTP, if you don’t already have it:

ntp server [vrf MANAGEMENT] aaa.bbb.ccc.ddd
[ntp source gig 0/0]
[ntp logging]

Setting the VRF and source interface are only needed if you are using a dedicated management interface. The “ntp logging” line is only useful for debugging information. Remember to TURN IT OFF once you’re satisfied that everything is working.

Doing a “show clock” will tell you whether or not NTP has been able to update your clock.

So how does this save you time?

Well, with properly annotated timezone information and a synchronized clock, you’ll spend less time debugging and converting times or correcting for a drifting system clock.

UPDATE – 26 November 2012:

If your device is already using DNS, rather than hard-coding an IP address for the NTP server, I suggest you pop on over to  For Canadian NTP servers, look here.

Using the NTP servers in a pool will make things a little more fault tolerant.  It will help with:

  • NTP server drift (yes, it does happen)
  • NTP server outages (this happens more regularly)

The config will end up looking more like this:

ntp server [vrf MANAGEMENT]
ntp server [vrf MANAGEMENT]
ntp server [vrf MANAGEMENT]
ntp server [vrf MANAGEMENT]