Our next topic of discussion
is how to bring up cereal point to point links.
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
router to one serial 010 is connected to a router ones serial 000
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,
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
A. C s u D issue provides a few functions to the router.
it provides what we call clocking
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,
A D. C. Device is the device that provides clocking.
A router, on the other hand, is considered a d T E device or a data terminating equipment device.
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
the show I p interface Brief command. In this command, you will see there are three fields
the 1st 2 fields. The 1st 1 is method this de nuits layer one. And the 2nd 1 is protocol.
This denotes layer to now. When you execute the show, I p interferes brief command. And you see
well, when you execute the show, I'd be interface brief command and
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
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
down. That means this is a layer to issue.
So down down there one issue up down there to issue
now with their two issues, that could be one of three things wrong.
So with lair to issues, you could either be missing
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.
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.
these two devices, these two routers are connected back to back.
This is what a serial cable looked like looks like and one end of the serial cable, if you will see,
or actually decides his D T.
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
whatever side gets connected to the D t and
becomes a DT side a C s u D issue is nothing more than a digital modem.
So a C S U D s. You will terminate a digital signal just like a regular modem will terminate an analog signal.
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.
DC devices provide the clocking, which is the physical bit transfer rate between two ends.
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.
the address. True 100.
I got 200.200 dot zero
However, if you thought about it, the mask is going to be slashed. 30.
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
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.
So you get a block size or four. So the first network goes from 40.0
2.3 dot one and to being the valid addresses and 10.3 being the broadcast.
Okay, now we'll move on to the lab.