Cisco IOS NTP Server

So configuring an external NTP Server is great to keep the date and time sync’d on evey device but what if you want to host your own NTP Server? This lab will discuss and demonstrate the configuration and verification of Cisco IOS NTP server.

Real World Application & Core Knowledge

If you’ve completed Lab 11-7 – Configure the Cisco IOS NTP Client then you’re probably pretty curious as to how R1 is configured as an NTP Server in that lab. When you think about it, its pretty cool to have a Cisco device as an NTP Server. In the real world you can have a high end Cisco 7200 or 7600 Cisco router as an NTP Server and have the entire infrastructure including the Windows or Linux network to obtain its time from the same NTP server in the network to ensure every device is in sync.

The configuration is quite simple, just a single command. To configure a supported Cisco device as a NTP Server you’ll use the ntp master # command in global configuration whereas the # is the stratum layer of the device. For example; ntp master 3 would configure the Cisco device as an Stratum 3 NTP Server.

In this lab you will configure R1 as an NTP Server and R2 as an NTP Client which queries its time from the NTP server; R1.

Familiarize yourself with the following new command(s) listed below;

Command Description
ntp master # This command is executed in global configuration and configures the Cisco device as an NTP Master server followed by the stratum number provided. Cisco devices will only allow the stratum # to be a configured as a value between 1 and 15.

The following logical topology shown below is to be used in this lab;

Lab Prerequisites

  • If you are using GNS3 than load the Free CCNA Workbook GNS3 topology than start devices; R1 and R2
  • Establish a console session with devices R1 and R2 than load the initial configurations provided below by copying the config from the textbox and pasting it into the respected routers console.

 

Lab Objectives

  • Manually configure the time and date on R1 to the current time and date.
  • Configure R1 as an NTP Master server in the stratum 3 layer.
  • Configure R2 as an NTP client using R1 as its NTP Server.
  • Verify that R2 is correctly syncing its time and date with R1.

Lab Instruction

Objective 1. – Manually configure the time and date on R1 to the current time and date.

R1#clock set 20:00:00 aug 26 2010

Objective 2. – Configure R1 as an NTP Master server in the stratum 3 layer.

R1#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R1(config)#ntp master 3
R1(config)#end
R1#

Objective 3. – Configure R2 as an NTP client using R1 as its NTP Server.

R2#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
R2(config)#ntp server 10.118.12.1
R2(config)#end
R2#

Objective 4. – Verify that R2 is correctly syncing its time and date with R1.

Read Me

You may need to wait a few minutes before R2 will synchronize its time with R1, so do not get discouraged if it does not sync immediately.

R2#show ntp associations

      address         ref clock     st  when  poll reach  delay  offset    disp
*~10.118.12.1       127.127.7.1       3    52    64  377     3.2   -1.38     0.9
 * master (synced), # master (unsynced), + selected, - candidate, ~ configured
R2#
R2#
R2#show clock
20:05:05.581 UTC Thu Aug 26 2010
R2#

As you can see from the NTP associations above that 10.118.12.1 is now the configured master and it is synchronized as its a denoted by the ~ and not the #.

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