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So here are the lab tasks and without further ado,

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let's head over to the lab environment and let's do

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the walkthrough of these lab tasks together.

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So I have just reset the lab environment using

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the reset option over here on the right and in a few moments,

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it'll be rocking and ready to go.

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All right, and here we go.

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I just wanted to get a quick peek at the topology,

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which is sitting right here on the desktop.

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Great, great, great. So our first task is set up R1 and R2 as

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a Stratum 1 NTP server.

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Effectively, they're going to trust their own time.

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So let's do that first. Let's open up server 1 by double-clicking
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So let's do that first. Let's open up server 1 by double-clicking

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here on server 1 NUG.

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Give that a moment to open up and that'll give us console access

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to all of our network devices.

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All right, so there we go. So here on R1,

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let's go and do a quick show NTP status to make sure we're

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starting off with nothing configured for NTP.

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Then we're going to configuration mode and type in NTP master

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and stratum 1 and boom, we're good to go.

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Now, debug is already enabled on this.

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I left it running from before.

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So when you start this lab, if you don't want debug,

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just do an undibug all right here from privilege mode and turn it off.
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just do an undibug all right here from privilege mode and turn it off.

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So we do a show NTP status.

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It basically says, yeah, I'm synchronized to myself.

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I'm stratum 1, reference is local,

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and we do a show NTP associations, a press center.

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So we're synchronized with a loop back address.

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We have reachability.

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We're syncing with ourselves and we're good to go.

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So we'll do the same thing over on R2.

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So we'll do R2 and VigT.

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Let's do a do, show NTP status.

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Just to verify that it's not yet configured and type in NTP master.
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Just to verify that it's not yet configured and type in NTP master.

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And even though the lab didn't say so, I'm going to go ahead and say this too.

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Just to give you a reinforcement that if this is a master level 2,

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then clients that synchronize with the server would be considered 3.

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So just add one for each hop in the path as you go down the line

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for devices getting their time from NTP servers.

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So now if we did a show NTP status and press center,

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we are a stratum 2 and we do a show NTP associations.

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It's going to confirm for us as well that we are ready to go.

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All right, so next, let's go ahead and set up R3 as a client to R1
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All right, so next, let's go ahead and set up R3 as a client to R1

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and R4 as a client to R2.

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So good to R3 first, NTP server, a 1.1.1.1 source interface,

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loop back zero, and we'll go ahead and say burst.

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And we'll do a similar treatment to R4, except on R4,

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we'll do a config T and NTP server.

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Point of loop back on R2.

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We use our source address of 4444, which is loop back interface,

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zeros address, let's also use the keyword burst, and we are good to go.
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zeros address, let's also use the keyword burst, and we are good to go.

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Then we'll verify our configuration.

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So back on R3, we'll do a show NTP status, press center, and it is synchronized

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.

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Now in your lab environment, that may take a minute or two to happen.

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So while that does, you can do a debug and watch the back and forth.

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We can also do a show NTP associations, press center, and

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it can also show NTP associations detail, and

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it'll give us a lot of the nitty gritty detail regarding that NTP association.

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So there's the command right there, and

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there's probably more than most people will ever need from the output.
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there's probably more than most people will ever need from the output.

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And I want to change the time just to verify that our clients,

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our three in this case, is going to follow this clock once again synchronizes.

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So we'll do a clock set, and let's do 20 colon 18 colon.

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Actually, you know what?

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We could set it like a whole year off, but

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let's just be aware that if we have a huge difference in time,

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it may take a long time for that synchronization to catch up.

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So let's go ahead and set it off for, let's say, I don't know how, 30 minutes.

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Let's say 20, 48 colon, 0, 0, and
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Let's say 20, 48 colon, 0, 0, and

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let's keep the same date, October 16, 2024.

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So now we do a show clock and show NTP status.

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Because we're a stratum one device is just thinks, okay,

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I'm going to trust my clock, whatever it is.

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So it's trusting the clock that it's 20, 48.

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And also I didn't change the local time zone with the offset.

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So that's UTC time.

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So if we go over to our three, who's synchronizing with R1,

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we do a show NTP status and press enter, it's saying unsynchronized.

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And that's because the time is different, and

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it's going to take a little bit for it to sync up with the server.
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it's going to take a little bit for it to sync up with the server.

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So we do a debug here of NTP all press enter, and

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we can see the message is going back and forth.

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All right, so we have some clock movement here.

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Also, let me go ahead and change the interval as well as to a show run,

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include NTP.

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[LAUGH]

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I said include, it should have been that,

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should be voice recognition, include NTP config.

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And I'll do an unall.

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And let me go ahead and do it config T and the same command,

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except I'm going to go ahead and change the timer, so

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make it a little bit faster.
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make it a little bit faster.

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So let's say min pull is four to the power four, and max pull is also

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made to the power of four and first just for friends.

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And that should make it happen a teeny bit faster.

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So let's go ahead and do a show NTP status.

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So boom, we are now synchronized with our stratum one server.

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If we do a show NTP associations, we can confirm that.

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Hence the little asterisk there to the left of our server.

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And then we do a show clock on R1 and R3.

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Let me go ahead and do it at the same time by using this icon up here.

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So we'll do a show clock, and I'm going to send that to R1 and
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So we'll do a show clock, and I'm going to send that to R1 and

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R3 at almost the exact same time with this tool here.

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Then script and so it's 2052 here on R3 and R1, 20.

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Okay, so it's slightly off, but you know what?

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As we take a look at that offset, that offset is going to get less and

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less as more packets go back and forth with NTP.

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So if we do a show NTP associations, this offset should reduce itself over time

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.

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And actually I would like to see that.

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So I'm going to go ahead and wait just a moment to show NTP associations again.
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So I'm going to go ahead and wait just a moment to show NTP associations again.

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And look at that, we now have less of an offset.

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So if we went back and we did a show clock on both R1 and R3 at the same time,

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they're going to be very, very close.

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So their show clock on R3, 2053, 24, and we'll go to R1 and 2053, 16,

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which is closer than it was a moment ago and as time goes on and

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we give it a few more packs to go back and forth,

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that synchronization actually should get closer and closer.

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So the offset used to be minus 196 in milliseconds.
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So the offset used to be minus 196 in milliseconds.

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Now it's in 67 milliseconds.

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All right, so let's take a look at our tasks.

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So we set up R3 as an NTP client.

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We set up R4 as NTP client R2.

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And the next task here is to set R8 as an NTP client to server 1 nog.

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And the reason I did this is I wanted to have you a little look and feel at

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what NTP looks like when you have different vendors.

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Because not every vendor influence NTP the same way.

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And for example, a Windows server, as it gets time from the internet,

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it has a certain stratum that it's using.
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it has a certain stratum that it's using.

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So I thought it'd be useful to go ahead and see this.

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So in our topology, that server, the server nog is right here.

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Server 1 nog is at 192.168.1.100 in the bottom right of our topology.

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It also happens to be the server that we're sitting at.

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So if you go to a command prompt here on this server, any type in time,

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and you press enter a couple times, it'll show us the local time.

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And that's with a Pacific time zone offset.

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So here on the Windows server, if we did a W32TM space/query,

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space/status, this indicates that we're getting our time from this time server
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space/status, this indicates that we're getting our time from this time server

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out on the internet.

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Here's the last successful sync time.

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And here it shows us a stratum 5 server.

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So if we are a client to this, we're not going to think stratum 5 is like the

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cat's meow because stratum 1 and 2 or 3 is going to be way better.

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But I'd like you to go ahead and be able to see that from the interface of a

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Cisco

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router that's trying to sync its time with this NTP server.

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So let's go back to our terminal windows here.

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This is a putty.

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And in our task bus, it'd R8 to be an NTP client.
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And in our task bus, it'd R8 to be an NTP client.

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So in our topology, R8 is right here off this gig 00 interface connected to

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that same subnet.

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So let's go to the right router, R8, and we'll do a show NTP's status, great,

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great, great.

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And config T. And let's also actually do a ping of 192.168.1.100 to make sure

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we can

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get there.

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Fantastic.

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And let's go to config T and do a NTP server, 192.168.1.100.

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And this is why it'd be useful to use certain options like version to specify

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what version

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of NTP want to use to be compatible with the server or to specify a key for
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of NTP want to use to be compatible with the server or to specify a key for

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authentication

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if we're using authentication.

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So I'm going to go ahead and say, let's do max poll, four and min poll of four.

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And let's also go ahead and say burst.

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And we'll say I burst.

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Now I burst is if it's not reachable sending multiple requests.

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But if it's reachable, the burst will cover that.

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So let's go ahead and press enter.

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And now that's done.

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Let's do a show NTP status press enter.

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So currently says unsynchronize, but check this out.
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So currently says unsynchronize, but check this out.

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It shows stratum six.

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So we know we had some connectivity.

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So we do a show NTP associations and press enter right here.

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Check this out.

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We have the tilde, which means we have full connectivity to that server.

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And the AstroSki indicates that we are synchronizing with that server.

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So currently here is our offset.

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And if we do a show NTP status, eventually we should be synchronized.

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Now look at this.

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We were, it did show a stratum of six because the server was a stratum of five.

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But now it's showing a stratum of 16.
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But now it's showing a stratum of 16.

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And this because it's still sorting it out, we haven't fully synchronized yet.

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So in this case, we might need to let this sit for five or ten minutes as it

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synchronizes.

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Also if the clock on the NTP server is flapping or fluctuating or goes forward

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and back and

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forward and back is not considered reliable.

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It could also cause this to take a long time before it's willing to synchronize

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with that

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destination.

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So I'm going to hit the upper key and do a show NTP status.

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And sure enough, it is not synchronized yet.

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Now also if you have two servers and one is, for example, a stratum one and the
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Now also if you have two servers and one is, for example, a stratum one and the

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other is

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a stratum five, it's going to choose your router is going to choose the one

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with the

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better stratum.

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So we could go in and we could say NTP server.

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Let's pick on one, one, one, one.

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And let's go ahead and say prefer and press enter.

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Now even if we didn't use the prefer, it would still prefer one, one, one, one

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because of

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the lower stratum.

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So in fact, let's go ahead and verify that by doing a no NTP server, one dot

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one dot one

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dot one, prefer and then with an NTP server, one dot one dot one and let's do a
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dot one, prefer and then with an NTP server, one dot one dot one and let's do a

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burst.

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And that looks great.

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And it's also do a ping to one dot one dot one dot one.

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Make sure we can get there and there's too many ones there.

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That's why it didn't like that.

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Sounds great.

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We'll do a show NTP associations.

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Now it shows us here that we have two configured, we have one, one, one, one

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with full connectivity

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and one 92, one state one dot one hundred shows us here that one, one, one, one

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is a stratum

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of one and the one and two, one state one dot one hundred is stratum of five.

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And so once we synchronize, we're going to be synchronizing with the one with
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And so once we synchronize, we're going to be synchronizing with the one with

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the better

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stratum, even though we didn't specify prefer.

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So let's do a show NTP status and still not synchronized.

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But again, we'll just give it a few moments and let it complete while that's

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ticking.

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Let's take a look at the rest of our tasks.

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So the last part of our lab here was to set our three and our four as NTP peers

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.

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So we're waiting for our eight to synchronize.

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Let's go ahead and set up our three and our four as NTP peers.

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So we'll get our three first and our three, let's do a ping to four, four, four

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, four,

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we'll source that from our loopback zero just to make sure we have connectivity
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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we'll source that from our loopback zero just to make sure we have connectivity

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and we

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do great.

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So we'll go to configuration mode and say NTP here and we'll put in four, four,

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four,

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four, and we'll say source loopback zero.

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That looks great.

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And then we'll do similar treatment over on our four.

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We'll show NTP associations and because our three made some requests in, we're

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aware of

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it, but we don't have it configured yet.

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So let's go ahead and do a config T and we'll say NTP and we'll say 3, 3, 3, 3,

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3 update

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source loopback zero too much BGP.
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X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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source loopback zero too much BGP.

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I'll say source loopback zero, fantastic.

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And then we'll do a show NTP associations.

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And now we have a little tilde next to it because we now have it configured.

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So notice that we lost our synchronization with 2, 2, 2, 2, but once it's

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sourced everything

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out, that should come back as well.

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So let's go to our three and take a peek.

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We'll do a show NTP associations and check it out.

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So our three has re-synced up with 1111.

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So if we did a show NTP status, we would expect to see synchronization with the
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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So if we did a show NTP status, we would expect to see synchronization with the

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NTP server

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and if we go to our four and let's see if our key show NTP associations, we

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should not,

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based on this output here, we should not yet expect to see synchronization.

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So if we did a show NTP status and press dinner, it shows as unsynchronized.

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However, that will correct itself in just a moment.

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So while we're waiting, we can do a debug NTP all and we can just wait for a

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message

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indicating it's synchronized.

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But right now we can confirm that we're communicating between 2, 2, 2, 2, and
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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But right now we can confirm that we're communicating between 2, 2, 2, 2, and

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our loopback address

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of 4, 4, 4, 4.

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So we'll do a show NTP associations.

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And once we have the little asterisk next to 2, 2, 2, 2, 2, that'll indicate

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that we

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have now synchronized with that server.

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So our offset right now is huge.

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And here we have a message here saying the clock is synchronized.

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But if we do an undibogal, look at that for a moment, it shows as synchronized

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with 3,

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3, 3, 3, 3.

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So now that it's settled, let's do a show NTP status and there we go.

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So we are now synchronized with 2, 2, 2, 2, and if we do a show NTP
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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So we are now synchronized with 2, 2, 2, 2, and if we do a show NTP

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associations and press

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center, it now has the asterisk next to that guy and it's showing it correctly

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as a stratum

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level 2.

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And 4, 3, 3, 3, 3, 3, it's still sorting it out because it's showing a stratum

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16, which

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isn't going to be correct for R3.

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And the reason I wanted to have you do this lab is I wanted you to see

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firsthand the fact

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that sometimes it takes a while for NTP to configure.

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By knowing a few of the show commands like show NTP status and show NTP

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associations and
WEBVTT
X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000

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associations and

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show NTP associations detail, we can help identify what's going on and if we

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need to,

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throw in the debugs for NTP all so we can see exactly what's happening at a

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very granular

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level.

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So thanks for joining me in this set of videos and I'll see you my friend in

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the next one

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soon.

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Until then, I hope this has been informative and I'd like to thank you for

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viewing.