After you perform a fresh install of NetMon, you must define an IP address for the Network Time Protocol (NTP) server used in your network to ensure that the timestamps in NetMon charts are accurate.
If you do not define an NTP Server, the displayed time values will likely be out of sync with your web browser. Events and log data will appear to have occurred in the past or even the future, and it will be difficult to ascertain the exact time a network event has occurred.
Open the NetMon Web Management interface.
On the top navigation bar, click Configuration, and then click the Time tab.
In the Primary NTP Server field, type the IP address of the main NTP server used in your network. The default is the address for the CentOS NTP server. If you do not establish an internet connection for the NetMon appliance and want to use a local NTP server, enter the address for that local server here.
In the Backup NTP Server field, enter the IP address for the backup NTP server (if used).
Click Apply Changes.
After defining and syncing with an NTP server, it can take several minutes for data to appear on NetMon dashboards.
In some environments, the default public NTP services are blocked, and you must use a valid internal NTP service.