Serial Countersignature Routing Made Easy

Serial countersignature routing

hi in this video I'm gonna introduce you to routing specifically the Cisco ipv4 routing table let's take a look okay so first of all remember what routing is all about as far as the routers perspective is the router receives an IP packet encapsulated in a data link framework uninflated and what it does is it's all about examining the destination IP address and looking that up in its routing table to see where is it gonna forward it next okay and you'll learn more about routing in later later videos and and that but let's kind of get past all this you've seen this animation in my other videos okay there we go alright so let's take a look at a Cisco IOS routing table alright so the command to examine a Cisco IOS routing ipv4 routing table specifically is the show IP route command so here we're looking at the routing table on router r1 now a routing table is going to show the networks that this router knows about and two types of networks those that are directly connected to a directly connected network means this is eight the router has an IP address on an interface and circle those there we go and get this whole thing so this router has three interfaces and each interface has beacon been configured with an ipv4 address and a subnet mask which tells the router that it belongs to three networks that's really no different than the PC the computer PC one has an ipv4 address and subnet mask and tells it what network it belongs to right but computers divide end-user devices usually belong to just one network the difference is the router will belong usually to multiple directly connected networks and not only that but it will also know about remote networks that's the highlight usually the idea of why we need a router is to learn about these remote networks and it can learn about remote networks networks that it does not have a direct connection to it can learn about them either statically and we'll take a look at this stuff later but a static routers where we have to manually configure main you'll have to tell the router what the what the remote network address is that's all we need is the network address and its subnet mask and what is the next hop address to get there that the other way that routers can learn about remote networks is dynamically using dynamic routing protocols like ew GRP OSPF and is is for example where the routers actually using the same dynamic routing protocol will exchange information about the networks that they know about and eventually learn about all the remote networks that all the routers are sharing in the same what we call routing domain alright so let's take a look at how to look at this routing table at least just the basics of it ok so directly connected routes ok so I mentioned that a directly connected route is a network that this router is directly connected to now you'll notice router r1 actually has three directly connected networks three interfaces it has three interfaces each with a different ipv4 subnet or network address yep so we have one here one here and one here so let's take a look at this one here the gigabit 0/0 so if you notice in the routing table here are the three one group two group three groups I'll talk about the C&L these codes I'm going to show here at a moment but the C means directly connected and the L means it's local address what is the actual address so let's take a look at one of the directly connected ones this one right here which is right here so first the status code I mentioned C means the the connected Network what network am i connected to and the L just means what's the what's my actual ipv4 address in this case of that interface so if we look here we can see that this first part is the network address in the connected and actually the actual ipv4 address itself the slash 32 let's not worry about that right now is known as a a hostmask but it is just that it's just telling the router this is my address but the network I belong to is 192 168 10.0 / 24 I am directly connected and analysis directly connected here and the actual interface is the gigabit 0/0 interface as we can see here okay otters can't do anything unless they already are dirt unless they're connected to at least one directly connected network it has to know about its own networks before it can learn about any other networks all right yeah that's they actually had an animation there but I don't think I need it alright let's go to the next one okay in this case a dynamic route so let's take a look in this case we're going to look on r1 and it has actually let me go right here so an r1 and we're going to look at this network this network in the routing table and the network we're actually looking at is 10110 which is this remote network so this is a network that our one does not have an interface directly connected to but it's actually learned about this network let me go to the next there we go it's actually let's take a look at this and a little bit more detail here okay so we're just looking at this information right here so how did it learn about this network well learned it using a dynamic routing protocol called e IG RP now the d actually doesn't stand for dynamic it actually stands for the routing protocol d 4e IG RP how'd they get that Oh long story but D actually stands for dual dua L the algorithm used by EIGRP doesn't use an e because that was used by another routing protocol not important but this is how it learned about the thoron in this case e IG RP here's the remote network okay so there's the network that it learned about okay these next time not real important yet but we'll talk a little bit about them this one does 90 is actually and you can you follow it here this is what we're doing here here for example the 90 that is known as the administrative distance okay not important at this point we'll talk more about it in later videos but it's just associated with our kind of a ranking of the source of the information in this case e IG RP this next value here this is the metric so AIG RP uses this combination of lowest bandwidth and cumulative delays don't worry about that what that is but how far away how far away is this network so that's the metric tells us this via IP address is the next hop address this is a timer that tells the the router how long have I known about this route and this gets refreshed continuously by the routing protocol and depends on the routing call don't worry about it too much right now this here is the exit interface so you'll see serial zero zero zero this is the exit innovates the interface it's going to go out of this is actually how the router knows what type of data link header and trailer to send it out of what is the encapsulation of of serial zero zero zero is at PPP point-to-point protocol then that's the kind of data link header trailer it's going to go into so this is kind of looking at the example of a dynamic route or a route learn dynamically in this case a routing protocol called e IG RP enhanced interior gateway protocol so many acronyms in this business but we'll learn about all that later but at least you've seen that this is how you can recognize a a remote route in the routing table alright remember those codes I talked about remember those codes that are down here well here they are I just hadn't shown them in the other routing tables just for to look to make things a little bit cleaner but they're always shown when you do the show IP route again we're looking at an ipv4 routing table let's take a look at some of those codes there's our c4 directly connected and you'll see it along with an L meaning the local interface IP address where's that D for EIG RP alright it is right well let's see where we're looking here it is ok d for EIG RP again why wasn't used because that was used by an older protocol called exterior gateway protocol that's not used anymore ok but you can see some of the other ways that we had a static route it have an S in it was learned by a routing protocol rip I would have an R in it all right so this this all what are these codes right Oh what happened there okay those codes were oh gosh okay I guess I can't go off the screen there okay but those codes right there all right well we're at the end of this video so you know all right so I hope this helps you begin to see what the routing table is all about again it's all about showing routes either kind dynamically or directly configured or actually both definitely you can see directly connected networks okay so you're always going to see these directly connected at least one directly connected networks and then as far as remote networks you're going to see either dynamic static or a combination of both and that tells us tells the router about networks that isn't that they are that it is not directly connected to it does not have a direct connection to alright so I hope this demystifies at least a little bit of the ipv4 routing table I know there's a lot more to it especially ipv4 but I think this is a good first step to help you understand