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In this example, router A is actually physically positioned between routers B and C; that's where it physically is. So it does have neighbors, router B and router C. But let's pretend we don't know anything about the "Show CDP Neighbors" command, so that's all we do; is just type in show (sh) cdp, and then neighbors (nei). It comes back and it says 'well I don't see anything'. I mean here is the capability codes, I could find routers, I could find transparent bridges, switches but here is all the devices I found, nothing. This is what I would have called them, there is the device id, local interface, the hold time, their capabilities, but the thing is, I didn't find anything. Well, the problem is that the interfaces aren't open. If I were to show the interface, I am going to type - sh ip int brie - which is show IP Interface brief, I can see that all of my interfaces are closed, including serial zero and serial one, which actually make the physical connections over to routers B and C. So let's open those up, so I am going to type conf t, in configure mode and then interface s0, and then all I am going to do is - no shut - it. So that will open it up, I am also going to do the same thing with Interface s1. Identify the interface, and then type - no shut. Now they will probably come up and then go right back down because the other side isn't open yet and as we said it before, that's perfectly normal. So this up-down state is fine. So, now we've got those opened up, so I type - end - get back to where I was and should I be able to see my neighbors now? Let's try - sh cdp nei - still nothing. Why? Because the other side isn't opened up either. So now what I am going to do is go to router B. And on router B, I am going to go ahead and open its interface that connects it to router A. And router B's interface that connects it to router A in this case is Serial 0. And I know that because I set it up. So I am going to type - conf t - and then - int s0 - and then - no shut - and type - end. Now notice it changed its state to up and then it stayed up. It went up-down but then a line protocol came up and it stayed up. Now let us go back to router A. And on router A, now I am going to type show CDP Neighbors. Notice now it found router B, it says - Oh, ok, now I see him, router B, if you go out, you are serial one, you will find there is a router out there. It is router B, it is platform 2520 and you are actually connected to his serial 0. So we can see router B now. What about router C? Can't see router C; that's because router C isn't up. In other words, its interface is not ready to be seen. So, router C's interface that is actually physically connected to me in this case is S1, so I am going to type conf t, Interface S1, and then no shut it. Now, router C ought to be able to if I type in a show CDP Neighbors of router C, it ought to be able to see its neighbor, router A. So I type - sh cdp nei - and it can. It says - Oh, Ok, Well, there is a router A connected to my serial interface one. There is a router with platform 2520 and if you go out there, you will find that you are connected to its port serial 0. That is how this thing is connected, so now let us go back to router A. So now if we take a look at router A and type show CDP Neighbors, we will find, Ok, good, we have got both neighbors that we can see. So, both neighbors router B and router C can now be seen using the Show CDP Neighbors command. Now if I wanted to see the details of these neighbors, then I could type - sh cdp nei det. And we can see now that router C is a platform 2520, capabilities - it is a router, interface - serial 0, port id, ok, that's in other words going out of my serial 0, my port id that I get to is serial one, that means we've connected to its serial one. So we can see a lot more information with 'show CDP neighbors'. Mainly the information that we are going to see is, here is the IOS 2500 Software, the version number. We can see all of that, and we are not directly connected to that router when we are seeing it. In other words, we are looking at the tool to find out information about the neighbors, and that is what this tool is all about. So 'Show CDP Neighbors', and 'show CPD Neighbors detail' can be great tools that we can use for troubleshooting and for Local Network Area Design. There are many tools and many rules that we need to know how to use, when we talk about Local Area Network Design. So in our next chapter, we will discuss LAN design. That's is next. There are many tools and many rules that we need to know how to use, when we talk about Local Area Network Design. So in our next chapter, we will discuss LAN design. That's is next.