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Our next topic of discussion
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is how to bring up cereal point to point links.
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Now, in our lap topology, if you have noticed we have a serial connection denoted by the thunderbolt in the Cisco vernacular between router to a one and router One
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router to one serial 010 is connected to a router ones serial 000
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Now, in the real world, routers are seldom connected back to back like this. What a router will do is have a serial connection to something called a C s u D s U,
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which is the termination point or the demarcation point for the I S P. That's where the ESPYs responsibility ends and your responsibility begins. The CSU D issue then connects to the I speak loud. And on the other end, there will be another CSU D issue. Connecting to your remote site router
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A. C s u D issue provides a few functions to the router.
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it provides what we call clocking
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or the physical bit transfer rate between the two end devices or between the two routers that at your local router and the remote router. The CSU D issue is also called a D C E device or a data connection equipment device or data connecting equipment. Device,
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A D. C. Device is the device that provides clocking.
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A router, on the other hand, is considered a d T E device or a data terminating equipment device.
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Now the CSU de ASU provides clocking for the router, which is the physical bit transfer rate between the C S, U. D s U and the router. As we do our lab, we will be exploring
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the show I p interface Brief command. In this command, you will see there are three fields
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the 1st 2 fields. The 1st 1 is method this de nuits layer one. And the 2nd 1 is protocol.
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This denotes layer to now. When you execute the show, I p interferes brief command. And you see
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well, when you execute the show, I'd be interface brief command and
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your due diligence. You have assigned an I p address and you have no shut the interface. But you still see down down. That means this is
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a layer one issue, so no amount a few troubleshooting sitting on console will help. You need to go check your cabling if you see
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down. That means this is a layer to issue.
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So down down there one issue up down there to issue
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now with their two issues, that could be one of three things wrong.
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So with lair to issues, you could either be missing
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keeper lives. So new people eyes are being sent. The second issue could be mismatch in copulation. And I will explain this further when we get to our lab and the third issue could be new clock rate set on D. C E.
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in the real world, As I said, CSU de issues, which actually the acronym stands for Channel Service unit data service unit Ah C s U D s. You will provide clocking.
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these two devices, these two routers are connected back to back.
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This is what a serial cable looked like looks like and one end of the serial cable, if you will see,
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or actually decides his D T.
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And then the other side actually says D. C. Whatever router gets this side of the cable, the one that says D C E becomes a D. C. And now must provide clocking and whatever side stays, DT
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whatever side gets connected to the D t and
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becomes a DT side a C s u D issue is nothing more than a digital modem.
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So a C S U D s. You will terminate a digital signal just like a regular modem will terminate an analog signal.
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Once again, the D C device, which could be a router if to routers are connected back to back and the D. C. Another cable goes into one of the routers that router becomes a D C Eastside or a C s u. D s u is a DC device.
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DC devices provide the clocking, which is the physical bit transfer rate between two ends.
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Now we're gonna move on to the lab, but right before we do, I want you to think about what the mast is going to be on this point to point link.
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the address. True 100.
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I got 200.200 dot zero
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However, if you thought about it, the mask is going to be slashed. 30.
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Remember, from our sub dating lecture yesterday, I said that this last 30 mask is used or point to point links. And I'm going to keep our outer one as 10.1. And I'm gonna assign 0.22 router to
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for the 202 102 100 0 slash 30 network. The two valid addresses are got one and dot, too, because the value of the last bit turned on for a slash 30 mask is four.
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So you get a block size or four. So the first network goes from 40.0
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2.3 dot one and to being the valid addresses and 10.3 being the broadcast.
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Okay, now we'll move on to the lab.