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What time is it I'm sure you agree that time is of great importance in the real world.
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And the same is true for networking.
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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
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in which time zone I'm based in the UK but you may be based elsewhere.
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So we're talking about 9:00 a.m. Eastern Time in the U.S. or Prep's Pacific time while we're talking
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about 9:00 a.m. U.K. time time is also of great importance when troubleshooting networking in this example
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I've got three routers Rato one Rohatyn wrote a three.
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And as an example if I type confetti and then controls it or control the Z notice the time on this router
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the log message is saying that the router was configured by the console but this router thinks it's
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in the year 2030.
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So it's done a bit of time travel the Shradha thinks that it's in the year 2002.
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So it's stuck in the past.
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I've got a router with the correct time in the UK but the wrong date the router thinks that it's based
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in the future the throttle has the correct time currently in the UK.
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This one doesn't.
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This router however has the wrong date.
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And so does this router.
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Now this becomes even more important when we are trying to troubleshoot an issue on the network.
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In this example all the Nabl OSPF on Route 2 it's already enabled on the other routers in the network.
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So we can see that a relationship was formed in the year 2030 and according to this site a neighbor
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relationship was formed in the year 2002.
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It's going to be very difficult to troubleshoot any kind of issue taking place between the routers in
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this network because the date and time is not synchronized on the roads.
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Now you can manually configure time on the road as so I could use the clock command as an example and
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set the time on the routers but that's not going to scale very well.
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If I have many many roads and in addition clucks a drift.
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So we ideally want to ensure that all the clocks on all the devices are synchronized to an atomic clock
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some way the protocol used for synchronization of time is network time protocol or a.p at the moment
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defined type show a.p status on router 1.
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We can see that a.p is not enabled a.p is not enabled by default on Cisco routers and switches you need
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to configure the devices to talk to a time source.
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Now in this example I don't have an atomic clock which I control my time from.
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You can as an example get a.p from various servers on the Internet.
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Here are some examples of anti-peace service available in the United Kingdom.
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Just do a search in Google or your favorite search engine for various pieces available online for security
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reasons you might prefer to get time from a local active directory server in your network rather than
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directly off the Internet.
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But in this network what we'll do is configurator three is a must to or what's called a stratum Rodda
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a.p has different levels.
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The lower the number the closer you are to a atomic clock source serratus three you would use a command.
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And I wouldn't do it right now because I want to set up some other values first that you specify a stratum
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value for the router.
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Once again the lower the number the closer you are to an atomic source.
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A.p uses a hierarchy of straught DMs way a router or a device for stratum 3 would get its time from
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a device with a lower number like one or two.
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Time would then be pushed across the network to multiple devices from one level to another a.p is once
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again used for clock synchronization between network devices or computer systems over a data network
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such as the Internet or our little network in the example.
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It's been around for a long time so since the 1980s it uses UDP port or use a datagram protocol port
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number 123 time can be sent using unicast broadcasts or multi costs.
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He has a picture of a U.S. naval master clock which has a stream of zero.
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In other words this is providing time to many of the devices using a whole Rockhill system stratum 0
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devices provide.
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Time to start them one which in turn provided to start them two three and so forth and so on stratum
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0 devices of very high precision time devices that have atomic clocks GPS clocks or other radio clocks.
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They're known as reference clocks and a.p straught them one all synchronized to within a few microseconds
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and teched to start them zero devices.
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They're referred to as primary time servers and then time filters down to other devices.
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So stratum two devices will carry stratum 1 and start them three will carry straught them to and that
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will continue up to the maximum of 15.
6809
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