NTP Client/Server 1

By certskills August 1, 2016 09:05


NTP makes me think of old spy novels and movies, where the team would set their analog watches to the same time, and say something like “On my mark, it will be 9:55… mark!”. NTP uses other mechanisms, of course, with protocol messages, and some devices declaring the time, with others adjusting their time to that declaration. Today’s lab lets you configure the basic time settings on a couple of routers, with two acting as NTP clients, and one as both a client and server.


Configure NTP for this network, with R2 and R3 as NTP clients. R1 acts as an NTP server for this network, while also acting as a client, adjusting its time from an NTP server in the Internet. The specific rules for this lab are:

  • Configure R1 to be the primary local time source (Stratum 3) using the IP address from its Loopback0 interface
  • Configure R1 as a client to obtain its primary clock from the NTP server pool.ntp.org
  • Configure R2 and R3 to obtain their primary clock from R1
  • Use R1’s loopback 0 address for any NTP configuration
  • Configure all devices to use Eastern Standard Time
  • Configure all devices to observe Eastern Daylight Time
  • Assumptions:
    • All device interfaces shown in the lab are up, working, and correctly configured with IP addresses
    • Routing is configured and working correctly
    • Name resolution is configured and working on all devices

Figure 1: NTP Topology

Initial Configuration

Examples 1, 2, and 3 show the beginning configuration state of R1, R2, and R3.

Example 1: R1 Config


Example 2: R2 Config


Example 3: R3 Config


Answer on Paper, or Maybe Test in Lab

Next, write your answer on paper. Or if you have some real gear or other tools, configure the lab using them.

To test your solution if you happen to try it with VIRL or real gear, you can use the show ntp status and show ntp associations command to verify the status of NTP and its associations. Keep in mind, however, that NTP synchronization on Cisco devices is not a fast process; it will take at least 10 minutes (or more) for all clocks to become synchronized (assuming your configuration was correct).

Do this Lab with Cisco’s VIRL

You can do these labs on paper and still get a lot out of the lab. As an extra help, we have added files for the Virtual Internet Routing Lab (VIRL) software as well. The .VIRL file found here is a file that when used with VIRL will load a lab topology similar to this lab’s topology, with the initial configuration shown in the lab as well. This section lists any differences between the lab exercise and the .VIRL file’s topology and configuration.

Download this lab’s VIRL file!

The virl topology matches this lab topology exactly.

Answers: SNMPv2c Secured with ACLs
CLI Miscellany 1
By certskills August 1, 2016 09:05
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