CCNA 2, Chapter 1: Routing Concepts

this is going to be the first video set of notes for CCNA - chapter 1 somewhat building off of what we did last time things have switched around in version 6 of CCNA - that we start with routing first and we're moving on to switched Network second so we'll be taking a look at some initial router configuration things we saw last class how routing decisions are made and router operation which will be more of the new material that we'll be seeing in this course so a lot of the stuff you'll recognize from CCNA 1 some of it will be a bit new like familiar things like router initial configuration things we've already done these are some things commands we've already issued already we've talked about characteristics of the network before the topology or layout of your network speed cost security implementation availability scalability how easy is it to expand and reliability of the network so why why routing why routing is because you wouldn't be able to communicate with other networks without routers doing their job you can see that it's going to route traffic between networks choose a best path for traffic to the next router along the path so you can get to your destination so your router is making those decisions that get you from one network to another efficiently ok we talked about the internals the hardware of a router before we have a CPU they have a operating system which is the Cisco IOS and the devices that we use different memory and storage we've discussed those and where things are stored there Ram ROM NVRAM flash drive a potentially hard drive so this is all stuff we've kind of seen before the components of your router what goes into it here's the physical layout of the router we've also seen this before you've got your console poor you've got your land interfaces your USB ports if you're looking to load an iOS or save one to a USB which is of course different from your console consoles what we're using to manage our Wix slots if you want to expand add some serial ports add some extra Ethernet ports whatever it is you want to do with your Wix slots so we've also discussed this and just kind of here for your reference I do not believe this comes up in testing for CCNA to anyway will come up in your CCNA general test more reviews more review materials we've talked about RAM and what's stored there your running config you're running iOS your IP and ARP tables your packet buffer you see that all here okay remember your startup config is stored in NVRAM and that then loads into RAM as you boot the router so that running config is in your rudder I mean sorry that running config using your RAM you never have a startup config file and RAM you never have a running config file and NVRAM okay we also have braum read-only memory that has your boot up instructions basic diagnostic software literate limited OS in case the router cannot load the full-featured OS which would be in flash down here okay so it takes you into basically a rom mom mode that allows you to recover a device that can't load its OS okay so again this is review from CCNA one here we talked about again routers inter connecting networks you've got routers on routers between possibly well potentially between you and whichever webserver web page you're accessing whichever file server you're accessing so those routers together are inter connecting your network each router has it having multiple interfaces that could be assigned to different networks per interface okay and we'll talk about some other things you can do with those interfaces if we go on through CCNA - routers do choose the best path to make your communication as efficient as possible you can see in the first bullet point that we have both static and dynamic routes and you can think of that just like static and dynamic IP addresses static our routes you're going to enter yourself manually dynamic are going to be learned well dynamically or automatically through some time dynamic routing process whether that be what we'll talk about some of them but you've got oh s PF e IG R P rip as dynamic routing protocols it could be used to learn about remote networks again we'll talk about that a bit later routers use the routing table to determine the best path to send your packets there are values that go into that okay again that comes up later in the chapter you've got a metric for distance between your two routers and the most trusted route in the routing table that we'll talk about which is a value for administrative distance that comes along later routers encapsulate the packet afford it to the into the interface indicated in the routing table you've got three packet forwarding methods basically if an order from oldest and slowest to newest and fastest and most efficient you've got process switching which would take every packet and if the process by the CPU in this control pain control plane looking for which interface that packets supposed to go out and then sending it out that interface on a one by one basis it was very slow so they improved that too fast switching which was actually used with process switching a fast switching were to fail or the next hop was not available in cash so basically what you see here is it would use a fast switching cash to store next hop information if a packet arrived in the control pane that matched an entry in the fest which in cash it would just go ahead and send it out the proper interface because it would have a match there if there was no match in the cash for fast switching then it need have to go back to the process switching process look up what interface it's supposed to go out and go so this is a way to speed up things a little bit by storing a next hop cash and packets matched that next hop cash and be sent a lot quicker the flow information is also stored from your packets so if another packet comes in from the stand same flow the CPU won't even be involved in the process for looking at the next hop in the fast switching cache it'll just be forwarded straight to the Kratt fast switching cache and sent out the proper interface so once you have packets that are all part of the same flow that speeds things up even more because you don't involve the CPU and all in the process you're just using this fast switching cache to use the next hop information to identify the next hop information if you don't remember what a next hop is the next hop member is just network to network router to router that's your hop each router would be considered a hop between your source for a packet in your destination so in case you didn't remember what a hop was that's what it is the last one the most recent and fastest and preferred a cisco packet forwarding method is cisco express forwarding so as it says this is the fastest of the forwarding techniques and you have this fib an adjacency table that's responsible for that the fib stands for forwarding information base and basically it control contains information for all the next hops on your network so basically all the possible destinations for a packet to go eventually once it learns all that information once all that information is learned then your CPU is taken out of the process you can just do some first lookups in this adjacency table and make decisions there because well every next hop basically is mapped so it makes things a lot quicker you're not having to make decisions using the CPU you're just using this table down here so that's why it's the most efficient of the packet forwarding methods the forwarding information base basically has like almost like a routing table it has all of your next hops and all the interfaces that packets might have to go out of without involving the CPU here we just have a basic topology of physical topology of how the network might be connected simple LAN and when connections for a home office a couple branches here basically you just have a bunch of Ethernet setups or wireless setups that connect you to your router or edge router which would be the batter in the edge of your network which will connect to the internet or to your ISP or the backbone of your network if you are a large corporation through when links typically serial so it's just a overview of a network nothing really to new or different there we've talked about default gateways before if you want to be able to get off your current network then you need an IP address subnet mask and a default gateway your default gateway again is the router interface that is connected to your network the IP address of that interface actually and your devices within a network of going to use that IP address to get off the network that's about it when documenting a network you want to make sure that all these items are in it your device names your interfaces your IP addresses and subnet masks default gateways so if you are documenting your network and how its set up that's what you want okay at minimum at minimum all right there are other things you could include but that's what you want at minimum again we have the concept of static versus DHCP static being that you assign manually your IP address subnet mask default gateway even DNS server dynamically well dynamically assign your IP address subnet mask default gateway idea in a server so dynamic automatically static is you are manually entering in your information yourself and we've seen this before enabling an IP on a host static versus dynamic you do want to know what the lights mean on your Cisco devices that one blink is 10 megabits per second two blinks for speed that is that's the speed indicator up here two blinks for 100 megabits three blinks for a thousand or gigabit speed on the speed link is the link active or inactive well greens active boss is not active and that's pretty much how it goes for the rest of these the L here is 4 into this L up there get the 2 here 2 there of course all right I do believe you can read so I will go ahead and go seed all right console connection you have available to you you've got a rj45 a db9 if you want to console in through your serial port ok we've gone ahead and looked at those console ports on our devices before that's again a serial tube basically a rj45 which is a Ethernet head on a port ok you also have a USB port you can use the console in then you see you can use a USB to serial to connect to that USB type a port that's a smaller USB port I can also use just a USB be to a cable that you also need a driver to make that happen it's available from Cisco comm the emulation program that you can use to console and putty teraterm we will be using putty in the class that's what we have installed on our computers enabling IP on a switch this is not new we've gone into interface vlan1 IP address yadda yadda no shutdown new if you want to manage remotely from outside the network then you need to have a default gateway in order to make that happen so we've done this command before that's review again work review commands enable password or your privileged exec mode pass where your line console 0 pass where your mine vty passwords done this all before so I'm just going to skip past that let you read that on your own configuring ipv4 on a router so we've done this as well going to your interface if you want to give it a description it's not a bad idea it's a good idea to give it a description can make life easier for you in the future give it IP address no shutdown similar to interface VLAN on a switch but you're using the actual physical interface on a router remember VLAN on a switch is not a physical interface oops wrong way there we go ipv6 well basically what we've discussed is that anytime you want to perform the same process for ipv6 that you did for ipv4 just change the command to say ipv6 rather than just IP and it should work ok so this is the exact same set of instructions it's only you're using ipv6 address here rather than IP address so same same instruction set in ipv6 to enable it on a router you'll need to let's see is that here yet I don't know well it doesn't look like it's here but to enable ipv6 on a router you're going to type you're going to use the command ipv6 unicast routing ok you are going to not sure what these commands are not spaced because if you try to configure an ipv6 address without having a space between ipv6 and address and you're going to run into problems so I'll go ahead and add those in there why don't I also this should probably be bolded because that's part of the link local creation alright so you type in ipv6 address me address you want slash the prefix at the end if you want to create an ipv6 address or use an ipv6 address with the EU I process that we've discussed before you type in your ipv6 address then the address and at the end you'd type in eui-64 to have you I generate that interface ID order interface identifier with the EU I process that uses your MAC address ok and then your link local address remember if you enable ipv6 on an interface it's automatically going to have a link local address in fact new enable ipv6 on your router I'm sorry just the interface if you do an ipv6 enable on the interface it's going to give you a link local address automatically if you want control over that link local address maybe you're going to have some logical or incremental ipv6 link local addressing scheme then you can configure it yourself statically otherwise again if you enable ipv6 on interface it's going to give it a link local address by default your loopback address you may have heard us referring to loop backs on your end devices on the router it's similar I want to be used for testing but it is also used for other purposes it's a way for the router to identify itself in case a link goes down that could cause problems for you so your your router will use that address as an address to identify the router in processes such as oh s PF you might have a link go down in that address basically it's not valid for the router the router can refer to itself as this loopback address at all times it is not associated with a physical port it is an internal address unique to the router okay so as you basically use for testing and management and a way for the router to identify itself in certain processes such as OSPF and the command for that is interface loopback whatever loop that 0 typically IP address then the subnet mask right after that and it doesn't have to be loopback so it could be loopback one and we'll discuss the different uses of loopback as we go through the materials or how it's incorporated I should say we've seen these commands before show IP interface brief there's an example there show IP route which is your routing table you've got show running config which does just that show interfaces which is going to show all of your interface information as well as your packet flow count for all interfaces on the device and show IP interfaces would you just for showing your ipv4 related information for all interfaces ok so those are our show commands we've seen them at one time or another in CCNA 1 one more thing on the these show commands there are in the readings some filters that you can apply to these show commands if you want to start in a certain point exclude some information include some information so make sure you take a look at that real quick at least in the readings whoa that I didn't mean to delete that it's not my intention here's your show IP route your ipv6 commands again just replace IP with ipv6 and you got that all right there's the filter command so you've got the pipe character after the command you type in section include begin you can see some examples of that happening down here you've got the section will show you a certain section brief include those that are up in the show IP interface brief okay you can see that the interfaces that were administratively down and I can't see all that here up there are excluded when you choose it include up you've also got as you can see a terminal length number you could add in to specify the number of lines to be displayed in your command some commands have tons of lines that they will attempt to show you so you can limit that if you want you may not need to because you do have the power to just press Enter or spacebar as many times as you want and then press any other key to stop the device from showing you more command so I don't know maybe that's a better feature or better use of your time we've actually worked with this history feature before how we've used it is when you type in a command and maybe it didn't work correctly or maybe you just want to repeat a command you press the up or down arrow key to see the previous commands by pressing up if you went too far you press down to move the other direction that can also be done with control P or control N and that is using the history command history feature if you want more commands to be remembered by default there's only ten commands from privileged exec mode the pound sign you can do a terminal history size and type in whatever size you want and it will store well more or less commands depending on what you type in here we've got 200 so it would store 200 commands so there's that alright I think that believes us at the end of this section not the chapter just yet don't get excited this section is going to go through routing decisions what happens when your packet arrives at a router and how it makes its decisions as to where it should go next so the first slide we have here is the switching function which basically don't think of switches it's not a not a switch layer to function it basically means yet your router is going to receive a packet and use its switching function to determine or move the packet from one interface to the next okay so what you get you receive the packet through what's called an ingress port and you send it through an egress port or an exit port so ingress incoming egress exort export whatever you want to call it okay so comes into this port the router is going to make a decision based on the encapsulating everything up to layer 3 and seeing which destination IP address this is headed for it's going to check that against this routing table perform a couple processes to make decisions and then send it out the appropriate interface okay so that's the switching function of receiving the packet then sending it on back out as it receives the packet is just going to look at this layer three information okay it's not going to change it layer three information doesn't change IP addresses don't change but it will change the layer 2 information because you know that MAC address is changed at every hop also you may need to re-inflate the frame to be sent over Ethernet versus sent over a serial link versus sent over I don't know Wireless or satellite something like that so that layer to information the leader to frame does get rien capsulated and changed the layer three portion is not going to be changed okay you do have mac addresses down here for each item except for the serial link serial mac information is not necessary for serial links so that's something to take note of this is just a point-to-point connection there's not any more than two devices in that connection so MAC addresses aren't necessary there all right move on we have talked about how MAC addresses are always going to have a destination of the next hop in your path so PC one as it encapsulates the frame is going to have a MAC address of r1 that is going to send to but a destination IP address of PC two all the way down here that IP address does not change we talked about that a bit okay I don't think there's really anything else to talk about on the slide so you can see you've got a MAC address table or I'm sorry an ARP table and a router MAC address table and a switch so you got our table and a routing table and that's what our ones using to make its decision basically here it has a ARP entry and it's ARP cache for the not for this guy here but for the next hop IP so it sees to get to said network that networks in its routing table it has to go to this next hop okay the next hop is r2 so in our ones art table for MAC addresses it has the MAC address for r2 so it has all the information and needs to build that frame and send it back over or send it along along to our to remember our ones receiving that packet D encapsulating there are three Rhian capsule a ting a new frame and sending that along the network to r2 and it's using this information in order to determine where it should be sending that data then we have the link between r2 and r3 as stated before we don't need MAC addresses in a serial link so that's empty it's just going to be sent along to the destination of our three over here without a MAC address entry because well that's the only direction it can go the only place to go it's a link to point-to-point link then at r3 it has a entry to reach PC too okay it's directly connected going out FA 0 0 so it's going to go ahead and send that on out and that was basically the end of that process we've got a general breakdown of routing decisions without getting into too many specifics here on this chart so the packet arrives on your routers interface the router is going to search this routing table for a match okay and we'll talk about how it searches for that match a little bit more in depth in a couple slides here but basically you're seeing does the IP address match the subnet or network of a directly connect the interface if it's a directly connected interface this is going to check the ARP cache and if there's nothing in the our cache for that IP address it's going to send out an ARP request if necessary and then forward it to the host on the local network or subnet I should say okay it's not directly connected is it on a remote network okay it's going to check for that if it is it's going to go ahead and encapsulate the frame and sort it out to the next hop IP address to get to the destination network if it is on a remote network so that's what's going to happen there and capsulate in the frame moving on out if it's not in the ARP table at all okay a on not the our cable the routing table at all no entry no match you've got is there a gateway of last resort available gateway of last resort basically means if nothing matches okay nothing matches a my routing table then I send all other traffic out some interface okay which would typically head towards the internet if there's no day gateway left resort configured it's just going to drop the packet if there is then it's been an encapsulate that frame send it on to the next hop do that to that gateway of last year power through the Gateway of last resort to the next hop okay hopefully that's clear that's all broken down in your readings as well as on so your best path is going to be determined by a metric values used to measure the distance between two a given network you'll see that metrics show up in a readout that we see in just a moment the best path to a network is a path with the lowest metric okay and that metric can be a few different things the other some protocols that use their own rules to build a metric the most simple of which is going to be ripped which is hop count okay hop count basically means how many routers are in between you and the destination network alright that takes them into account none of the speed of the links between you and a destination network just how many hops you could be hopping on to a network with 10 megabit per second speed but because fewer hops you're going to use it with rip so it's not always the greatest okay you've got open shortest path first which is a protocol that is used between all different types of devices cisco brocade it's not exclusive to anyone okay so it's cost based on cumulative bandwidth from source to destination basically based on speed ok so that's going to be a bit more reliable then rip in most cases then you have enhanced interior gateway routing protocol our AI GRP that is cisco proprietary and takes into account bandwidth delay load and reliability you want to remember that those are the items involved in the IG RP and well how each one of these calculates they're metric because that those are definitely test questions all right so load balancing load balancing means if it said a metric to get to a certain destination is the same between two routes okay so they're both equal speed what your devices will do is send basically equal amounts of data on each path so neither one's getting overloaded and hopefully that's causing optimum speed and reaching your destination because you're balancing the load of work between both paths so that's what load balancing is based you can see it improves never conformed perform as an equal cost load balancing can be configured to use both dynamic routing and static dynamic standing Rohtak all protocols and static route I'm not sure if it'll come up in a test or not but the only protocol that lets you do unequal cost unequal cost load balancing is AI GRP administrative distance this is basically well the trustworthiness of a route or the effectiveness of a route again lower is better and you can see the default numbers administrative distances associated with your different types of routes with a connected static GI GRP OSPF so on and so forth and these are default administrative distances they actually can be changed we won't be doing that just yet but they can be they can be changed annually and router operation we have talked about writing tables before and you've got direct directly connected and remote routes we solve those with a cnl entry for the directly connected I think we only saw D for EIG RP in your routing table before there's also an O for OSPF that you'll see okay so we did use the show IP route command oh by the way routing tables stored in RAM that's probably something you want to know - it's stored in RAM we use the show IP route to show the routing table we have here local routes that are added to the routing table when an interface is configured so just by interfaces configured you see an L entry there your local route we've got a directly connected interface which we saw has a C in front of it typically where it does have a C in front of it and that's added to the routing table when the interface is configured and active static routes are going to be configured by well you that's what static means in your routes and in your IP addresses if you manually configured it then you have dynamic routes that are learned automatically based on whichever protocol is being used so if the I GRP OSPF implemented you can learn your routes that way as well and here we just have a breakdown of what each one of those letters pretty much means over OSPF D for eigrp are for rip C and L we've seen before connected in local so there's that those are the ones we'll see most at least at this point are the LC our Oh Wendy over there and I believe we've seen this before in C in a one not going to go over everything again you can see how it was learned of the administrative distance and the metric to reach whichever network what it learned it from the elapsed time since the network was discovered and the interface over here so you've got the legend down there we've gone over that before a newly deployed router without any configure a basis has yes an empty routing table you haven't given any IP addresses you haven't done a no shutdown on any interfaces so your your routing table is empty you do a show IP route it's very sad then when you have a directly connected entry you can see the network that is directly connected okay for in this in this case it's the 192 want to take ten zero network that's the network and then you have the local address for your interface on that network so on that network my router is okay sharing something to sounded like a bee flying around in here but I guess it's not anyhow there is the address of your link that is connected to that local network okay so the interface g00 is 192.168.1 and that's its address on the 192.168 10.0 network all right and well there's more on the directly connected networks in your routing table you've got it beginning at the gateway of last resort and just showing your directly connected routes that's really not too important right now all right in ipv6 you're directly connected routes again I'm going to have a C and an L same concept sees the network L is the actual address of your link on that network okay you could see a unicast address or link local address here if you have a FF 80 at the fe80 you can have a link local address there all right and then we come to static routes all right here we have static routes that are going to be well configured by you all right it's a path between two networks how you get from one place to another that you just enter in yourself the commands to configure a static route it's just going to be to type in from global config IP route then well the network that you're trying to reach and its subnet mask okay so that's we got network and mask there after that you are going well either use the next hop IP address or the exit interface you're going to use to get to said network okay usually it's going to be a little easier just to type in the eggs interface so an example of a static route is so I'm going to bring this up over here and give me a second here we go all right so here's two different ways you could write in a static route you can go IP route this is their network you're trying to reach and you could just use the interface as part of the entry or you can go I P route network you're trying to reach and then use the next hop IP address okay which would be the own r2 here trying to get to the two to five that's where you're going to get to the eleven network that's your next hop so you type in that number there again I think it's going to be easier for me if I just have two types at zero zero zero instead of writing out a whole IP address but up to you up to you how you want to do things okay you also have a default route that well if nothing matches in your routing table you're going to use that default route it's going to send you basically to the de Gateway of last resort and we'll hope for the best as you send traffic over there okay so you can see that we've got a static route set there for d8 a default static route for the Gateway last resort that has a s in front of it whenever it's configured and that's something that well you're going to want to configure pretty much all the time okay so c0 if you have no matching your routing table you want your traffic to go somewhere okay otherwise you're only communicating with networks that you've learned or are directly connected to okay a couple other static routes entries you've got down here you can see how they've been typed in this one was configured with the interface this one was configured with the next hop IP so you've got that all right your default static route your default static route in ipv6 remember your default static route is all zeros in ipv4 ipv6 it's all zeros as well but a colon colon represents all zeros in ipv6 so that's what you get here that's your stat your default static routes going to be going to be going out of serial zero zero zero there so so you got there and you can see how you configure other static route entries again it's just instead of IP route ipv6 route you're typing in the network that you're trying to get to then you can type in either the next hop IP or the interface it just looks a little Messier because our brains don't like ipv6 that much just yet and then we have dynamic routing which is automatically learning about path to different networks so dynamic routing is used by routers to share information about the reach ability and status of remote networks performs network discovery and maintains routing tables okay routers have converged after they finished exchanging into information and updating their routing tables basically they know about all the routes around them so this is a pretty well simplified version of dynamic routing basically our one saying hey r2 I know about these networks and how you get to them and here's that information what do you know r2 says I know about the network's over here so use me to get there I'm your next hop and I'm going to take the information you've given me and put it in my writing table so you're exchanging information to build a reading crowding table as to how to get to different networks dynamically which is good or has advantages over static because if there's multiple ways to get to a network and one goes down the dynamic routing protocol can automatically get around that and choose a new best path to a certain network whereas if you had a static entry then your static path went down nothing's going to happen you're kind of stuck all right a Cisco router can support a variety of different dynamic routing protocols you got these if you're looking to see which protocols are supported by your Cisco Cisco router you can type router question mark and it will show you all those protocols that are that are supported and we're not really not configuring these things yet we will soon not yet not yet but you can see what those will look like in a routing table you've got again d4 EIGRP so you'll see that there and yeah those are just well entries in your routing table for it and dynamic routing protocols we've got ipv6 dynamic routing protocols got rip and G for next generation OSPF v3 not d2 or v6 but v3 for ipv6 okay rather than just regular OSPF and EIGRP is just er GRP but four v6 and if you want to know what ipv6 routing protocols are supported you've got the ipv6 router question mark you see here as we move along to saying what those entries look like any are adding table and then you know I think two different with that although with the v6 you will have the link local um showing up as to how you know how to get to a certain network you use that certain link local address rather than to the global unicast so don't let that throw you off the link local address will pop up every now and then and then we are done with this chapter all right so that's chapter one team review concepts also throwing a lot of routing table and static dynamic [Music] directly connected entries in your routing table so a little bit of new stuff but I'd say oh no 30 percent review anyway that's it for the video

Channel: CeeJayII

Views: 52,723

Keywords: CCNA 2, CCNA, CCENT, cisco, network, academy, routing

Id: voj31y4j8v4

Length: 45min 49sec (2749 seconds)

Published: Sat Apr 01 2017