NTP (Network Time Protocol) is an application layer protocol used for time synchronization between hosts on a TCP/IP network. The goal of NTP is to ensure that all devices on a network agree on the time, since even a small difference can cause problems. NTP uses a client-server architecture; usually with one host being configured as the NTP server, and other hosts on the network are configured as NTP clients.
Cisco routers can be configured as both NTP clients and NTP servers. To configure a Cisco router as an NTP client, we can use the ntp server IP_ADDRESS command:
Floor1(config)#ntp server 192.168.0.100
To verify NTP status, use the show ntp status command:
Floor1#show ntp status Clock is synchronized, stratum 2, reference is 192.168.0.100 nominal freq is 250.0000 Hz, actual freq is 249.9990 Hz, precision is 2**19 reference time is DE4AB2B7.0000037A (18:49:27.890 UTC Thu Apr 5 2018) clock offset is 0.00 msec, root delay is 0.00 msec root dispersion is 0.02 msec, peer dispersion is 0.02 msec.
To configure your Cisco router as an NTP server, only a single command is needed:
After entering this command you will need to point all the devices in your LAN to use the router as NTP server.