All language subtitles for Free-CCNA-NTP-Day-37-CCNA-200-301-Complete-Course_en

This is a free, complete course for the CCNA.

If you like these videos, please subscribe\n

Also, please like and leave a comment, and\n

In this video we will cover NTP, Network Time\nProtocol.

All computers have an internal clock, including\nnetwork devices.

For a variety of reasons that we will cover\n

devices have an accurate clock that is synchronized\n

NTP is covered in exam topic 4.2, which says\n

NTP operating in client and server mode.

Over the next section of the course I will\n

This video on NTP will be the first.

Here’s what we’ll cover in this video.

First I’ll briefly explain why time is important\n

Then I’ll show you how to manually configure\n

Then we’ll cover the basics of NTP, Network\nTime Protocol.

Finally I’ll show you how to configure NTP\non Cisco devices.

Make sure to watch until the end of the video\n

ExSim practice exams simulate the style and\n

I used them myself, and I highly recommend\nthem.

If you want to get Boson ExSim, follow the\n

First, let me briefly introduce time on network\n

All devices have an internal clock.

That includes routers, switches, your PC,\n

In Cisco IOS, you can view the time with the\nSHOW CLOCK command.

So, I used this command at 12:16 AM, 0 seconds,\n

On Saturday, December 26th 2020.

The time zone is the default of UTC.

Remember that, the default time zone is UTC,\n

If you use the SHOW CLOCK DETAIL command you\n

In this case it is using the hardware calendar\n

The hardware calendar is the built-in internal\n

This is the time source by default.

However, notice this asterisk here.

It means that this time is not considered\nauthoritative.

The device isn’t confident that this time\nis accurate.

The internal hardware clock of a device will\n

Now, why is it important to have an accurate\ntime source?

From a CCNA perspective, or really the perspective\n

reason to have accurate time on a device is\n

Devices keep logs of various events that occur,\n

OSPF neighbor relationships being formed or\n

Syslog, the protocol used to keep device logs,\n

But let’s take a quick look at some device\nlogs now.

The command to view a device’s logs is SHOW\nLOGGING.

Let’s say I’m a network admin and I got\n

So, to investigate I log into one of the devices\n

Here’s a portion of the output from one\nof the devices, R2.

Notice this series of messages about OSPF\n

There are multiple messages about neighbor\n

You can see the timestamps here, indicating\n

Note that I will cover these log messages\n

don’t worry about the details for now.

I just want to show why time is important.

Anyway, I then checked the device’s clock\n

Then I log into R2’s neighbor 10.0.0.6,\n

Here’s some of the output from SHOW LOGGING.

You can see those same messages about an OSPF\n

states, and also some messages about an interface\n

However, the timestamps show a totally different\n

After checking the clock I realize that R3\n

This is going to make it much more difficult\n

In this case, it’s a fairly simple issue.

We can see that an interface going down caused\n

But when you have to troubleshoot more complex\n

of messages, it gets much more difficult and\n

So let’s see how to manually configure the\ntime on a device.

You can manually configure the time on the\n

I entered CLOCK SET and used the question\n

Using the format of hours, minutes, seconds,\nI entered the time.

The next option is either the day of the month\n

You can enter them in either order.

I entered the day first, and then the month.

I entered the year, 2020, and checked the\noptions.

CR, carriage return, basically means press\n

After entering the time I checked with SHOW\n

The time source also has changed to ‘user\nconfiguration’.

Notice that all of these commands are done\n

These clock configurations aren’t part of\n

Here’s one more point a lot of people might\nnot be aware of.

Although the hardware calendar (the built-in\n

clock and software clock are separate and\n

So let’s see how to configure the hardware\nclock.

You can manually configure the hardware clock\n

So, from now on I will use the term ‘clock’\n

device, and ‘calendar’ to refer to the\nhardware clock.

So, the command syntax is the same as CLOCK\n

Set the time, and then either the day or the\nmonth.

I set the day, and then the month, and the\n

Then I set the year, and then used the command\n

Typically you want to synchronize the clock\nand calendar.

I can’t think of a good reason not to sync\nthem.

Use the command CLOCK UPDATE-CALENDAR to sync\n

The calendar will update its time to match\nthe clock.

Or, use the command CLOCK READ-CALENDAR to\n

In this case the clock will update its time\n

First let me demonstrate CLOCK UPDATE-CALENDAR.

I viewed R2’s clock, and the time was about\n

However the calendar was about 12:00AM.

So, I used the CLOCK UPDATE-CALENDAR command.

And now you can see the calendar has been\n

Next let’s see the opposite situation, when\n

The clock says it’s about 12AM on September\n6th 1993.

The calendar has the correct time of 2:55PM\n

So, I used the command CLOCK READ-CALENDAR.

And the clock updated its time to match the\ncalendar’s time.

Next let’s see how to configure the timezone.

You can configure the time zone with the CLOCK\nTIMEZONE command.

First I used the DO SHOW CLOCK command to\n

Notice I used DO SHOW CLOCK from global config\n

That’s because the timezone is configured\n

the running config of the device.

So, here’s the CLOCK TIMEZONE command.

The first option is the name of the time zone.

This is just a word, the device doesn’t\n

So, I configured JST for Japan Standard Time,\n

JST is 9 hours ahead of UTC, so I entered\n

For JST I don’t have to enter the minutes\n

Notice the time zone has changed from UTC\n

This is because the previous time configurations\n

When changing the time zone to JST, 9 hours\n

But currently the time actually is about 3:15\n

and now it displays the correct time in the\ncorrect time zone.

The time zone is important because, as you’ll\n

adjust each device to the correct time zone.

There’s one more aspect of manual time configuration\nto cover.

That is daylight saving time, also known as\n

Not all countries do this, but in many countries\n

You can configure Cisco devices to do that\nautomatically.

Now, I live in Japan at the moment and Japan\n

use my home country of Canada as an example.

In most parts of Canada we set the clocks\n

at 2AM, and then set the clocks back one hour\n

The command to configure this is CLOCK SUMMER-TIME,\n

The first option is the name of the time zone.

My time zone back in Canada is EST, but during\n

Then we can set a specific date to change\n

but the more useful option is the second one,\nRECURRING.

This makes summer time start and end on the\n

After recurring, we specify which week in\n

In Canada it starts on the second Sunday of\n

Next is the weekday, so I entered Sunday.

After that it’s the Month, March for Canada.

Finally the time, I entered 2AM.

Okay, so that’s all for the start time.

Now we enter the end of daylight saving time\nin the same order.

1 for the first week, the weekday, Sunday,\n

Optionally you can specify the offset, but\n

what most countries use by default.

So, that’s all for the command.

This command is a little long, too long for\n

some of the output is cut off and can’t\n

CLOCK SUMMER-TIME, the time-zone name, RECURRING,\n

and the end of daylight saving time.

Okay, that’s the CLOCK SUMMER-TIME command.

So, that’s all for manual time configuration.

Here are the time commands we just looked\nat.

The CLOCK SUMMER-TIME command is a little\n

Just remember that for the ‘start’ and\n

Okay, let’s move on to the next topic.

And the next topic is the main topic of this\n

Manually configuring the time on devices is\nnot scalable.

In a large network, manually configuring the\n

PC, phone, etc, would be a huge task and a\nhuge waste of time.

Not only that, the manually configured clocks\n

NTP allows automatic syncing of time over\n

The device you’re using to watch this video\n

For example, on my Windows 10 PC you can see\n

That is an NTP server somewhere on the Internet.

And actually, you can configure this.

So, for example, if I wanted my PC to synchronize\n

This point is separate from the topic, but\n

resolved to IP addresses using the protocol\nDNS.

DNS will be covered in a future video, it’s\n

In the CLI of my Windows PC, I used the command\n

It contacted the DNS server I’m using, which\n

Then Google’s server gave me the answer.

The actual IP address of the Windows NTP server\nis 20.43.94.199.

I tried the same with Google’s NTP server,\n

Again, my PC asked the Google DNS server for\n

You can see four IPv6 addresses and four IPv4\n

Anyway, DNS will be covered in detail in another\n

So, NTP clients request the time from NTP\n

It’s possible for a device to be an NTP\n

So, it will sync its time to a server, and\n

These are rough numbers, they can vary, but\n

millisecond if the NTP server is in the same\n

to the NTP server over a WAN or the Internet.

Some NTP servers are ‘better’ than others.

The ‘distance’ of an NTP server from the\n

The farther away from the reference clock,\n

If the stratum level of a server is high,\n

NTP uses UDP port 123 to communicate.

Remember that one, in addition to the ones\n

Let me briefly introduce those reference clocks.

A reference clock is usually a very accurate\n

Reference clocks are stratum 0 within the\nNTP hierarchy.

They are as close to the time source as possible,\n

NTP servers directly connected to reference\n

You’ll see more about this NTP hierarchy\nin the next slide.

Here’s an example of a reference clock,\n

Cisco devices aren’t able to get their time\n

like this, but they can get their time from\n

This diagram demonstrates the NTP hierarchy.

These reference clocks are stratum 0, they\n

Navy clock we saw in the last slide.

The servers directly connected to those reference\n

Then, stratum 2 NTP servers get their time\n

And stratum 3 servers get their time from\nstratum 2 servers.

That’s how the NTP hierarchy works.

However, stratum 15 is the maximum.

Anything above that is considered unreliable\n

Another aspect of NTP shown in this diagram\nis NTP peering.

Devices can peer with devices at the same\n

This also acts as a backup, in case they lose\n

This mode is called ‘symmetric active’\nmode.

So, Cisco devices can operate in three NTP\nmodes.

Server mode, Client mode, and symmetric active\nmode.

They can be in all three of those modes at\nthe same time, too.

And finally, an NTP client can sync to multiple\nservers.

For example, in this diagram this stratum\n

Here’s some extra terminology you should\nknow.

NTP servers which get their time directly\n

They sync their time directly to a reference\n

NTP servers which get their time from other\n

They operate in server mode and client mode\nat the same time.

So, servers with stratum 2 or above are secondary\nservers.

Okay I think that’s enough lecturing, let’s\n

more aspects of NTP as we configure it on\nsome Cisco routers.

Here’s the network topology I’ll be using\n

I’m showing you an actual screenshot of\n

Through this Internet cloud in GNS3, these\n

the real Internet, and in this demonstration\n

This is a cool part of GNS3 that isn’t available\n

Now, you might be wondering why this point-to-point\n

That’s just how this cloud is configured\nby default in GNS3.

For a real point-to-point connection to an\n

So let’s configure R1 to sync to Google’s\nNTP servers.

Once again, here’s the NSLOOKUP I did for\nGoogle’s NTP servers.

I’ll be configuring all four of these IPv4\n

NTP SERVER, followed by the server IP address.

The order of these doesn’t matter.

R1 will ask all of them for the time and select\n

And the one it selects to sync to might change\n

start slowing down or it stops responding\naltogether.

So, it’s best to specify multiple NTP servers\n

Now, if you want to manually make the device\n

can add PREFER to the end of the command.

So, this would make 216.239.35.0 the preferred\n

But for this demonstration, I didn’t use\n

we’ll see which of these NTP servers was\nselected as the best.

Here’s a very important SHOW command for\n

It shows all of the NTP servers we just configured.

Now, you don’t have to understand all of\n

Notice the asterisk next to 216.239.35.0,\nmeaning ‘sys.peer’.

This means that this is the NTP server that\n

This plus sign next to the other servers means\n

The tilde next to all of the servers simply\n

in the previous slide with the NTP SERVER\ncommand.

If you see an NTP server marked as an ‘outlyer’\n

sync to that server, for example R1 might\n

The details of these states are beyond the\n

Here you can see the reference clock of each\nNTP server.

All of these servers are using Google’s\n

That is a stratum 0 reference clock, so here\n

four of these servers have a stratum level\nof 1.

I used the SHOW NTP ASSOCIATIONS command again,\n

as the server it wants to sync to.

This will constantly change as R1 continues\n

Now let’s look at another useful NTP SHOW\ncommand.

That command is SHOW NTP STATUS.

There’s a lot of information here that you\n

Clock is synchronized, that’s good.

It means that at least one of the NTP servers\n

Stratum 2, this is R1’s stratum.

Because R1 is synchronizing its time to Google’s\n

server itself with a stratum level 1 higher\n

So, that’s why R1’s stratum level is 2.

Finally you can see the address of the reference\nclock.

This time it’s not 216.239.35.0 or .4, it’s\n.12.

Now let’s check R1’s clock and calendar\nagain.

The time is correct, however the time zone\nis not.

NTP uses only the UTC time zone.

You must configure the appropriate time zone\non each device.

I haven’t configured R1’s time zone yet,\nso I’ll do that.

I also used the DO SHOW CALENDAR command.

Notice that the time is not synced up with\nthe software clock.

NTP doesn’t update the calendar by default,\n

So, I configured my time zone of JST here\non R1.

Then I used the NTP UPDATE-CALENDAR command.

This configures the router to update the hardware\n

So I checked the clock and the calendar again,\n

You might be wondering why you would want\n

The hardware clock tracks the date and time\n

When the system is restarted, the hardware\n

So, it’s a good idea to keep the hardware\n

Now we’re going to move on to R2 and configure\n

Usually in a small network like this you’d\n

to public NTP servers like Google’s.

But for the purpose of this lesson I’ll\n

But before doing that, I’ll configure a\n

Note that I’ve configured OSPF in this network\n

including the route to R1’s loopback interface.

I also instructed R1 to use loopback0 as the\n

So, any NTP messages it sends will come from\n

Why configure a loopback interface?

Well, let’s say I configured R2 to use 10.0.0.1,\n

In normal situations it would be able to send\n

But what if the interface failed for some\nreason?

R2 would suddenly lose its NTP server, because\n

on the status of R1’s G0/1 interface.

But what if we configure this loopback interface\n

Even if the closest path to R1, via R2’s\n

a route to 10.1.1.1 to R2 and therefore R2\n

I gave a similar demonstration of why loopback\n

Basically they are useful because they provide\n

it which isn’t dependent on the status of\n

Okay, so on R2 I configured NTP SERVER 10.1.1.1,\n

Notice the asterisk next to 10.1.1.1, that\n

R1’s reference clock is displayed here.

This is the IP address of one of Google’s\n

And here R1’s stratum level of 2 is displayed.

Google’s reference clock is stratum 0, Google’s\n

I checked with DO SHOW NTP STATUS.

R2’s stratum is 3, because it got its time\n

R2’s reference of 10.1.1.1, R1, is displayed\nalso.

As a reminder, remember to use the NTP SOURCE\n

as the source of NTP packets on R1, if you\n

Finally I configured NTP on R3.

By the way, I configured a loopback interface\n

I configured both R1 and R2 as NTP servers\n

Between R1, 10.1.1.1, and R2, 10.2.2.2, which\n

R1 is the preferred NTP server.

It’s because of the stratum levels.

NTP servers with lower stratum levels are\n

So, they are considered more accurate.

Okay, so I’ve shown you how to make a Cisco\n

For the next few concepts I’ll use a different\n

If a device is already syncing to an NTP server,\n

acts as an NTP server too and other devices\ncan sync to it.

But what if there is no NTP server to sync\nto?

You probably still want the devices in the\n

is slightly inaccurate compared to the actual\ntime.

So, how can you manually configure a Cisco\n

it isn’t synced to another NTP server?

As the description says it makes the device\n

So, on R1 I used the NTP MASTER command.

Notice that I can specify the stratum of R1.

However I chose to just enter the command,\n

The address of R1’s NTP server is now 127.127.1.1.

Remember, the entire 127.0.0.0/8 address range\n

Loopback addresses and loopback interfaces\n

are similar, so don’t confuse the terms.

Loopback interfaces are virtual interfaces\n

to other devices using OSPF etc.

Loopback addresses are a totally different\n

to the local device and can’t be reached\nby other devices.

Basically, R1 is using itself as its reference\nclock.

Anyway, the stratum level of this server is\n7.

So, what is the actual stratum level of R1?

I used SHOW NTP STATUS to check, and the answer\nis 8.

So, remember that the default stratum of the\n

And I configured R2 and R3 to use R1 as their\nNTP server.

We’ve already covered that enough so let’s\n

So let’s configure symmetric active mode\nbetween R2 and R3.

They both have a stratum level of 9, so they\n

They can become peers and help each other\n

case they lose contact with R1.

The command to configure symmetric active\n

So, I configured R3 as R2’s peer.

And here is the entry for R3 in R2’s NTP\nassociation table.

R3’s reference clock is R1, 10.0.12.1.

Its stratum level is 9, because R1’s is\n8.

I did the same configurations on R3, specifying\nR2 as the peer.

Again, the reference clock is R1 and the stratum\nlevel is 9.

Okay the final topic for today is NTP authentication.

I can’t say for sure if this is on the exam\n

But I recommend learning these few commands\n

NTP authentication on the CCNA exam.

NTP authentication can be configured, but\nit is optional.

You don’t need to configure it.

It allows NTP clients to ensure that they\n

They will check that the server is using the\n

Here’s how you configure NTP authentication\n

First, enable NTP authentication with the\n

Then you create the authentication key or\nkeys.

You can create multiple keys, but don’t\n

So, for the ‘key-number’ field just use\n

Then you have to specify which key or keys\nare trusted.

Creating the key uses one command, NTP AUTHENTICATION-KEY,\n

Finally you must specify which key to use\nfor each server.

This command isn’t needed on the server\nitself.

Now let’s look at these configurations on\nR1, R2, and R3.

On all three routers I used NTP AUTHENTICATE,\n

of jeremysitlab, and NTP TRUSTED-KEY 1.

Then on the clients R2 and R3 only, I used\n

So, they will use key number 1, which is jeremysitlab,\n

I also did one extra command, NTP PEER, followed\n

This adds authentication to the peer relationship\n

Okay, so that’s all you need to configure\n

In addition to the manual time configuration\n

To help you review, here are the commands\nwe looked at.

If you don’t remember any of these, go back\n

Before moving on to the quiz, let’s review\nwhat we covered.

We looked at why time is important for network\ndevices.

The main reason from a CCNA perspective is\n

Then we looked at how to manually configure\n

Then we looked at the basics of NTP and how\nto configure it.

We covered a lot already, but there is so\n

However I think the information we covered\n

Make sure to watch until the end of the quiz\n

ExSim for CCNA, the best practice exams for\nthe CCNA.

Okay, let’s go to quiz question 1.

Which of the following commands will cause\n

Pause the video to think about your answer.

The answer is C, CLOCK READ-CALENDAR.

This will cause the router to adjust its software\n

D will do the opposite, it will cause the\n

A and B are not valid commands.

Which of the following commands can be used\n

Pause the video to think about your answer.

The answer is D. From global config mode,\n

Unlike some other time commands, this command\n

You cannot configure the time zone with the\nCLOCK SET command.

Okay, let’s go to question 3.

Which of the following commands was configured\non R1?

Pause the video now to think about your answer.

The answer is A, NTP MASTER 9.

Because the address of R1’s NTP association\n

that the NTP MASTER command was used.

However, in this case the stratum must have\n

The default stratum of the NTP MASTER command\n

In that case, however, SHOW NTP ASSOCIATIONS\n

In this output the stratum is 8, so the command\n

Regarding option B, the command NTP SERVER\n

You can’t manually configure a loopback\n

it displays this way when the NTP MASTER command\nis used.

Which of the following commands configures\n

Pause the video now to think about your answer.

The answer is C, NTP SERVER 216.239.35.0.

It configures R1 to become a client of the\n

A, NTP PEER, configures symmetric active mode.

B, NTP MASTER, configures server mode.

And D, NTP CLIENT, is not a valid command.

Which of the following commands must be configured\n

Before I show the answers, let me say that\n

multiple answers, the question will always\n

But for a challenge, let’s try ‘select\nall that apply’.

Okay, pause the video to think about your\nanswers.

The answers are C, D, F, and G. C enables\n

D creates the authentication key.

F specifies that the key is a trusted key.

And G specifies the key to use with the server.

Okay, that’s all for the quiz.

Now let’s take a look at a bonus question\n

Okay here's today's Boson ExSim practice question.

Which of the following is enabled on a Cisco\n

from global configuration mode?

Here are the options A, static client mode.

Okay pause the video now to select the best\nanswer.

So this is closely related to one of the quiz\n

When you issue the NTP SERVER command you're\n

So you are making the router an NTP client.

So the answer is either A or C. Now in my\n

I don't think you need to know this for the\nCCNA.

So the regular kind of NTP client that you\n

So that should be the correct answer.

So here is Boson's explanation.

If you want to read about the broadcast client\n

Okay, so you can pause the video to read that.

And down here are the bottom there is a reference\n

Okay so that's Boson ExSim for the CCNA.

As I have said many times before, these are\n

So if you're preparing to take the real CCNA\n

If you want to get Boson ExSim, please follow\n

There are supplementary materials for this\nvideo.

There is a flashcard deck to use with the\nsoftware ‘Anki’.

There will also be a packet tracer practice\n

That will be in the next video.

Sign up for my mailing list via the link in\n

the flashcards and packet tracer lab files\nfor the course.

Before finishing today’s video I want to\n

To join, please click the ‘Join’ button\nunder the video.

Thank you \nto Biraj, Magrathea, Samil, Junhong, Njabulo

Benjamin, Tshepiso, Justin, Prakaash, Nasir,\n

Value, John, Funnydart, Velvijaykum, Mark,\n

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