Some points to remember, clients adjust their time from what they hear from an NTP server, NTP server
supply time to clients,
they don't adjust their time to the clients
the clients adjust their time to the servers.
An NTP client server device, such as router 2 in our example, got time from an NTP server.
So it was synchronizing to router 3 and then provided time to router 1.
NTP needs what is called a trusted clock source.
Ideally, you would get this from a lower stratum device, such as a domain controller in your network
or an NTP server on the Internet. In the lab
We didn't have an NTP server that we were connecting to
so I configured router 3 as an NTP master so that it trusted its own internal clock as the clock
source.
Once again, in the real world, that's not ideal.
You should get your time from a better time source.
A stratum level or stratum as some of you may pronounce it, defines the quality of the time
source the lower the number, the better the time source.
A stratum is a device that has an atomic clock or a GPS clock or radio clock.
In other words, it's a very good reference for time.
NTP is quite simple to configure once again to set up a server or stratum device, you would use the
command NTP master to specify a loopback interface, which is better than using a physical interface
because loopbacks don't go down.
Use the NTP source loopback zero command to specify a server.
Use the command NTP server and specify the server so the server command makes router 2 a client, the master
command means that router 3 is the trusted source of time.
Router 2 however, is also a server providing time to router 1 because router 1 is pointing
to router 2 for its time.
So we didn't configure router 2 as a server, it was simply configured as a client
but it started providing time to router 1 when router 1 queried it.
It can also use its own clock as a backup if it loses connection to router 3.