What time is it I'm sure you agree that time is of great importance in the real world.
And the same is true for networking.
If I asked you to have a meeting with me tomorrow at 9:00 a.m. one of the first questions is 9:00 AM
in which time zone I'm based in the UK but you may be based elsewhere.
So we're talking about 9:00 a.m. Eastern Time in the U.S. or Prep's Pacific time while we're talking
about 9:00 a.m. U.K. time time is also of great importance when troubleshooting networking in this example
I've got three routers Rato one Rohatyn wrote a three.
And as an example if I type confetti and then controls it or control the Z notice the time on this router
the log message is saying that the router was configured by the console but this router thinks it's
in the year 2030.
So it's done a bit of time travel the Shradha thinks that it's in the year 2002.
So it's stuck in the past.
I've got a router with the correct time in the UK but the wrong date the router thinks that it's based
in the future the throttle has the correct time currently in the UK.
This one doesn't.
This router however has the wrong date.
And so does this router.
Now this becomes even more important when we are trying to troubleshoot an issue on the network.
In this example all the Nabl OSPF on Route 2 it's already enabled on the other routers in the network.
So we can see that a relationship was formed in the year 2030 and according to this site a neighbor
relationship was formed in the year 2002.
It's going to be very difficult to troubleshoot any kind of issue taking place between the routers in
this network because the date and time is not synchronized on the roads.
Now you can manually configure time on the road as so I could use the clock command as an example and
set the time on the routers but that's not going to scale very well.
If I have many many roads and in addition clucks a drift.
So we ideally want to ensure that all the clocks on all the devices are synchronized to an atomic clock
some way the protocol used for synchronization of time is network time protocol or a.p at the moment
defined type show a.p status on router 1.
We can see that a.p is not enabled a.p is not enabled by default on Cisco routers and switches you need
to configure the devices to talk to a time source.
Now in this example I don't have an atomic clock which I control my time from.
You can as an example get a.p from various servers on the Internet.
Here are some examples of anti-peace service available in the United Kingdom.
Just do a search in Google or your favorite search engine for various pieces available online for security
reasons you might prefer to get time from a local active directory server in your network rather than
directly off the Internet.
But in this network what we'll do is configurator three is a must to or what's called a stratum Rodda
a.p has different levels.
The lower the number the closer you are to a atomic clock source serratus three you would use a command.
And I wouldn't do it right now because I want to set up some other values first that you specify a stratum
value for the router.
Once again the lower the number the closer you are to an atomic source.
A.p uses a hierarchy of straught DMs way a router or a device for stratum 3 would get its time from
a device with a lower number like one or two.
Time would then be pushed across the network to multiple devices from one level to another a.p is once
again used for clock synchronization between network devices or computer systems over a data network
such as the Internet or our little network in the example.
It's been around for a long time so since the 1980s it uses UDP port or use a datagram protocol port
number 123 time can be sent using unicast broadcasts or multi costs.
He has a picture of a U.S. naval master clock which has a stream of zero.
In other words this is providing time to many of the devices using a whole Rockhill system stratum 0
devices provide.
Time to start them one which in turn provided to start them two three and so forth and so on stratum
0 devices of very high precision time devices that have atomic clocks GPS clocks or other radio clocks.
They're known as reference clocks and a.p straught them one all synchronized to within a few microseconds
and teched to start them zero devices.
They're referred to as primary time servers and then time filters down to other devices.
So stratum two devices will carry stratum 1 and start them three will carry straught them to and that
will continue up to the maximum of 15.