Network Routing Protocol Design - Complete Course [CCNP ENCOR/Network+]

[Music] hi this is david voss ccie11372 and in this video we're going to cover routing protocol concepts to introduce you to routing protocols for your ccda exam cisco wants you to be able to identify the attributes of routing protocols so you can make the correct design decisions the fundamental question is which routing protocol should you use when answering that question you must keep in mind the following characteristics of routing protocols and cisco wants you to remember all of these first is scalability how large is your network now how large will it become this is important because there are versions of rep where actually all versions of rip have a maximum hop count of 15 routers ospf and eigrp scale much better and bgp is the primary routing protocol used on the internet so obviously it scales very well and many companies in fact use bgp internally for that reason vendor interoperability will you be using all cisco routers on your network or will be a blend of cisco and non-cisco why is that important well rip and ospf work fine regardless of vendor and now even cisco has taken steps to ensure eigrp can be used by any networking vendor the question is do they support it rip and ospf and bgp most likely eigrp maybe or maybe not by non-cisco vendors it staffs familiarity with the protocol you and the it staff at your company might be much more familiar with one routing protocol over another i worked at a company where we had an internal debate over eigrp versus ospf and the tipping point for the conversation was what protocols did the engineers already know or want to learn better it was ospf and therefore that's what we went with as far as our design decision that was the tipping point you will have the same debates internally and should be prepared for this in your decision making process speed of convergence a benefit of dynamic routing protocols over static routes is the ability for dynamic routing protocols to reroute around network failures when this failure occurs the network recalculates and reaches a steady state condition this is called the state of being a converged network the amount of time for the failure to occur is called the convergence time now some routing protocols have faster convergence times than others this is important because when a network is not in a steady state data can be dropped or looped within the network you should know that because rip and bgp might take up to a few minutes to converge by contrast ospf and eigrp can converge in just a few seconds the capability to perform summarization large enterprise networks can have routing tables with many route entries and network summarization allows multiple routes to then be summarized into a single route advertisement so it reduces the number of entries in a router's routing table that eats up less memory and also cpu because it reduces the number of network advertisements that need to be sent and that can obviously increase convergence time as well here's a perfect example let's say we're looking at the routing table of a core router and it knows about all the branch offices and let's say there are 255 branch offices and each are a lot of the slash 24 and they're assigned to 192.168 x.04 network now sure the core router has individual entries for all of these routes and knows how to reach all of them through separate interfaces or tunnels but all these routes do not need to be passed individually throughout the network onto a neighbor through a route advertisement they can be summarized using one summary route 192.16800 16. so as you can see using summarization we're saving a lot of memory and cpu by simply summarizing all of these routes into one single route interior or exterior routing a key term you need to understand is a s which stands for autonomous system and this is a network under a single administrative control a network might be a single as and when it connects to let's say another network let's say an internet service provider then it's connecting to a separate as when you're selecting a routing protocol you need to determine is it running inside your network or will you be running it with somebody outside of your network to answer the question as to what routing protocol you should run you need to understand if you need an igp an interior gateway protocol or a egp an exterior gateway protocol an igp exchanges routes between routers in a single as common igps are eigrp or ospf and then rip and isis are also used but not as much today the only egp in use is bgp but please note that bgp is sometimes also used as an interior gateway protocol as well there are two types of routing protocols the first type is distance vector distance vector routing protocols send a full copy of the router's routing table to directly attach neighbors now obviously this is not very efficient because it's sending information to a neighbor even if the neighbor already has that information this can lead to slower convergence time with slow convergence time you then can introduce routing loops the routing protocols that are considered distance vector are rip and eigrp there are two mechanisms that you can use to deal with routing loops that cisco wants you to know the first is split horizon this prevents a route learned on an interface from being advertised back out that same interface i'll show you a diagram in a minute so this makes more sense and then there's poison reverse which causes a route received on one interface to then be advertised out the same interface with an infinite metric so that nobody actually wants to use it but let's go ahead and take a look at the diagram so we can better understand the issue with routing loops and distance vector routing protocols and then what we can do about it with split horizon or poison reverse as you can see here we have a basic point-to-point network router 1 connecting to router 2 over serial interface and then a network 192.168.1.0 24 which is then advertised out serial 0 over to router 1. router 1 then learns that route and places it in its routing table as you can see here with a metric of one one hop now what if ethernet zero on router two were to go down and the network were no longer available the problem with distance vector routing is that router one is going to send its full routing table over to router 2. well router 2 does not know about 192.168.1.0 anymore so when it receives the subnet advertisement from router 1 of 192.168.1.0 it's going to accept it and place it in its routing table with a metric of two and this is where we introduce routing loops router two will then forward traffic over to router one router one thinks it can reach that network via router 2 and traffic will then loop between the two routers this obviously is not ideal now you've already learned about the two solutions to deal with that and you'll need to know it for your ccmp exam split horizon will prevent a route learned on an interface but from being advertised back out that same interface and then poison reverse which causes a route received on one interface to be advertised out that same interface with an infinite metric the next type of routing protocol you need to be aware of is the link state routing protocol routers send link state advertisements or lsa to advertise the networks they know how to reach so they don't send the full routing table just the networks they know how to reach and only when there is a change in the topology they only exchange full routing information when two routers initially form their adjacency but from there on out it's on a need to know basis the routing protocols that are linked state routing protocols are ospf and isis and the final type of routing protocol you need to know is path vector bgp is path vector and it includes information not just about the neighbor but the exact path that packets take to reach a specific destination network so when you do look at bgpu advertisements you can see exactly over what autonomous systems that traffic is flowing over so you've learned about the role of routing in an enterprise network and the different layers of enterprise network design and then you learn the basic characteristics of routing protocols which is really going to help you as you solidify your foundation and now you move forward in your ccmp studies i'm sure you're going to do great and continue on with the video series and good luck to you in your studies [Music] hi this is david voss ccie11372 and in this video you're going to learn about rip design specifically we're going to first learn about rip version 1 so you can lay a foundation for understanding rip version 2. since that is the version most commonly used today and if you were to design a network using rip most likely that would be the version you would choose so let's begin with rip version one now the major drawback of rip version one and why many don't use it today is that it has classful behavior meaning that it does not send back subnet mask information now if there is no subnet mask information in the updates then it assumes that any network is staying within its class full boundary which in as you know in most networks today that's rare as you can see here each class has a range of ip addresses that it would support and if it were to remain on classful boundaries that would mean that you would not be able to provide vlsm or break down these assigned subnets into smaller subnets so for example if you were assigned a network in the class a range let's say a 10 dot network you would not be able to break your 10 dot network down into smaller subnets so later in this video we will talk about auto summarization and that if it summarizes on a classful boundary specifically with 10 dot networks you can have routing problems so often you will find that you will want to turn off auto summarization in rip version 2. another issue with rip version 1 is that it broadcasts updates so it uses unnecessary bandwidth but it also means that routers that are not even running rip will constantly receive rip updates even though they won't process them because routers that run rip will broadcast and mount all interfaces modern routing protocols use a multicast approach in order to solve this issue by sending updates only to routers that really need to receive them rip version one does not allow authentication so there is no element of security that can be added to the routing protocol to ensure that it is not sending information to devices that should not receive it when examining rip version 2 you can see that many of rip version 1 shortcomings have been addressed rip version 2 has a classless behavior meaning that subnet mask information is sent in updates so vlsm can be achieved version 2 also supports authentication to ensure that the person you are sending the information to is the person authorized to receive that information now in addition to plain text passwords the cisco implementation provides the ability to use md5 authentication md5 is a hashing algorithm that takes a variable length string of text and produces a fixed length 128 bit output the advantage of hashtag plain text is that the original message cannot be reconstructed even with the knowledge of the hash algorithm now with regards to advertisements rip version 2 multicasts routing updates instead of broadcasting them as rip version 1 does so this allows for the efficient exchange of routing updates another special feature of version 2 is automatic summarization feature which is applied to prefixes on classful boundaries this behavior is a double-edged sword because it can induce problems in real world scenarios let's look at the following example router 1 connects to the following networks 10.10.10.0 and 10.10.20.0 and 10.10.30.0 router 1 connects to router 2 and then onto router 3 which has connectivity to the 10.40.0 and 10.10.50.0 networks there are also other networks between the routers such as 172.1600 and 192.168.000 notice the change in classful boundaries that makes rip automatically summarize the networks behind router 1 and router 3 as 10.0.0.0.8 toward router 2. this can lead to a problem or it will lead to a problem router 2 will receive the same route from both directions if it receives a packet destined for 10.10.10.0 it can send it in both directions based on the automatically summarized prefixes it received this problem is called discontiguous subnets and it's generated by the automatic summarization behavior of the routing protocol that aggregates those subnets solutions for this problem involve not using discontiguous subnets in different areas in the network topology or disabling auto summarization let's take a look at the rip version 2 message format the rib version 2 message format takes advantage of the unused fields in the version 1 message format by adding subnet masks and other information let's go through some of the key attributes of this message the command field indicates whether the packet is a request or response message the request message asks that a router send all or part of its routing table response messages contain route entries the router sends the response periodically or as a reply to a request version specifies the rip version used 2 for rip version 2 and 1 for rip version 1. afi field specifies the address family used rip is designed to carry routing information for several different protocols each entry has an afi to indicate the type of address specified the afi for ip is two route tag route tags provide a method for distinguishing between internal routes which are learned by rip and external routes which are learned from other routing protocols you can add this optional attribute during the redistribution of routing protocols ip address specifies the ip address of the destination subnet mask contains the subnet mask for the destination now if this field is zero no subnet mask has been specified for the entry next hop indicates the ip address of the next hop where packets are sent to reach the destination and metric indicates how many router hops to reach the destination the metric is always going to be between 1 and 15 for a valid route since 16 would indicate an unreasonable unreachable or infinite route another aspect about rip that you need to know is that it relies on a series of timers for its operations as described here the update timer this is where updates are sent and they're sent every 30 seconds by default invalid the route is invalidated if no update was received before this timer expires flush timer determines the time a route gets flushed from the rip table and hold down timer updates are not accepted for a route that keeps getting a bad metric and finally the sleep timer which can add delay to triggered updates the hold down and sleep timers are cisco specific and are used to enhance the rip functionality they were not originally specified in the rfcs for rip in summary here are some key points about rip version 2 that you need to memorize for your ccda exam it's a distance vector protocol which uses udp port 520 it does not scale well since the maximum hop count is 15. periodic route updates are sent every 30 seconds to a multicast address 25 routes are allowed per rip message or 24 if you're using authentication and obviously it supports authentication subnet mask is included in every route entry it's a classless protocol it does support vlsm and the metric for version 2 is router hop count now all of these points you need to memorize for your ccda exam this video has given you a good base foundation for preparations for your ccda if you can memorize what you've learned in this video you should do very well when asked questions about rip and how and when you would use it in a network design good luck in your studies [Music] hi this is david voss ccie11372 and in this video you're going to learn about eigrp design we're going to do a high level eigrp overview in this video and then we're going to talk about the eigrp components you're going to see this constant theme of these four components so first there are eigrp messages that are unique to eigrp there's a unique eigrp algorithm there are tables that are again unique to eigrp that you need to know about and then finally you need to know that eigrp supports independent modules so there are multiple there's multiple support for multiple different network layer protocols now the way we're going to approach this is again it's a high level overview of concepts that are unique to eigrp so we all know that eigrp can support vlsm for example but many routing protocols can so we're not going to dig into vlsm and eigrp we're going to talk about things that are unique to eigrp now for to understand eigrp we first need to understand igrp igrp came out in 1986. it is an interior gateway protocol that was once very popular distance vector a distance vector routing protocol and it used four key attributes to develop um this distance information on how to choose the best path so it looked at the link and then it said how much available bandwidth is there how much delay how much load and how much link reliability is there on this link path or on the multiple links to my path well e-i-g-r-p is still an interior gateway protocol and it is still a distance vector protocol although it many times in the past it had been referred to as hybrid but those days are pretty much gone distance vector is what it's classified as but it has can improve convergence in operations so it uses the dual diffusing update algorithm and i'll show you about that in a few minutes and then again it has multiple unique tables eigrp which assists in the operations and enhances the operations and then again it supports multiple network layer protocols so how does eigrp actually work well i'll tell you what let's go ahead and open up the hood and take a look underneath eigrp has four basic components and these should already start looking familiar to you it has messages so messages flow to and from neighbors eigrp neighbors there's five different types we'll dig into that in a little bit eigrp has the dual algorithm the dual algorithm takes the information from those messages and then processes best path and possible best path then all the information from the messages and the algorithms get put into tables so these eigrp tables hold the data from the algorithm and the messages and then finally the modules these protocol dependent modules support a variety of network layer protocols so we're not limited eigrp is not limited to just ip so with regards to messages there are different types of packet formats there's five different types of packet formats first there's the hello message a hello message is basically a query out to anybody who'll listen asking if anybody's out there so our router running eigrp sends hello packets by default and it will send those packets out and hope for a return reply and when it gets a return reply it'll get that update and that update contains all the messages or all the routes that want to be shared via eigrp update messages are messages with a lot of routing information in them and then there's the acknowledgement message which surely you know about from other protocols but it's simply acknowledging that yes i've received your message and that's key to the reliable nature of eigrp which we'll talk about in a minute there's a query message so if eigrp loses a route and does not know how to get there anymore it will query its neighbors saying do you have any information about this route because i'd like to get that information and then if a router does have information on that route or on that path it will reply back saying yes i do have information and here it is so these five messages can be broken out into two categories some that are reliable and some that are not reliable the reliable messages are use reliable transport protocol and this is unique to eigrp but rtp basically makes sure that packets get to where they're supposed to go in order so an unreliable packet is a hello message that message is not reliable but the update message from an eigrp router does use rtp so it is sequenced and there are acknowledgements so there is an acknowledgment to that message but the acknowledgement itself is not reliable then there's the query message remember the query is to ask do you have information about this route and that is that uses rtp and the response to that query the reply also uses rtp so three different types of messages use rtp the update the query and the reply and i think that's critical to know for your exam now let's talk about the eigrp algorithm which is dual now to understand dual you need to understand what successor and feasible successor routes are think when you think of successor just think of success that's the best path so if eigrp loses connectivity to the best path it will then run the dual algorithm and ask is there a feasible successor is there a second best path and if the dual algorithm states yes there is a feasible successor a second best path it will then promote that second best path to the to the best path so that becomes the successor once it's it's the successor it is then installed into the routing table so for example it would be installed into the ip routing table and then the router would begin to use that new path so this chart gives you an overview of base a high-level overview of how the dual algorithm runs but it's important to know these concepts of successor and feasible successor as you move forward with eigrp and how dual uses that information now eigrp uses specific tables to help make it run and one of the tables that eigrp uses is called the neighbor table now a neighbor table is exactly what you think it is it's a table that is comprised of a listing of all the eigrp neighbors so for example we have a hub and spoke design here we have router a router b and router c and router a and router b are both running eigrp router a sends out a hello packet and router b responds back as well and they've established a neighbor relationship and router a sends out a hello packet router c does the same and they've established their eigrp neighbor relationship so once that happens router a begins to build out its neighbor table by identifying each router that each neighbor by ip address so for example router b is 172 16 1.1 and he gets placed into the neighbor table and then router c is 192.168.10.2 and he is placed in the router table as well so router a now has two neighbors and they are both listed in its neighbor table but there's also other information in the neighbor table as well and it the router a also wants to know what interface are these routers off of so router b is off of serial one router c is off of serial two so should i need to forward them uh traffic or i know exactly which interface they will be exiting and then finally there's other information that is entered into the neighbor table there's quite a bit actually but for the sake of this high level overview let's just talk about hold time because this is a key concept when you program hold time on a router it's not local you're not changing the whole time locally that information is actually forwarded over to your neighbor router so here we have router c who's changed his hold time to 10 seconds he forwards that over to router a and here we have router b and let's say he's going to change his hold time this information that they're changing from the default it gets inserted into the neighbor table on router a and remember hold time is basically telling the router if you don't hear from me in this amount of time consider me down and flush the routes that you receive from me so it's important to remember hold time is configured on router c and router b but the actual numeric change occurs on router a in the neighbor table now there's definitely other attributes that are in the neighbor table and we will definitely go over those in future videos but on a high level overview of eigrp you need to know about the ip the interface and the hold time counter and just remember hold time defaults are is 180 seconds for low bandwidth links and 15 seconds for t1 or higher so that'll come up again again and you'll probably be asked about that as well but there are other eigrp tables that you should also be aware of and a key table to know about is the topology table topology table contains all destinations advertised by neighboring routers this includes remember the successor and feasible successor routes the best path to a destination and the next best path respectively so topology table is key for eigrp to run now remember within topology table you can see the route tags so in eigrp you can actually perform route tagging and all you really need to know for now is that you can identify routes by their origination which allows for custom routing so you can tag those routes with a manual entry so that's all you really need to know for now but getting back to eigrp tables now here's an example we have again a hub and spoke design router a router b in router c now router a is going to build out as soon as it enables eigrp it's going to build out these eigrp tables and one of the tables again is going to be this topology table the topology table is going to contain critical information for eigrp to run and make the choices upon what the best best path is going to be so in the topology table it's going to insert routes that it learns from router b and router c and then it's going to ask now that i know about this route which neighbor did i learn it from and then finally it's going to say all right i know the route i know the neighbor i learned from what metric should i assign to it which way should i send traffic or forward traffic so in this example the route itself let's say we'll do a 10.1.1.0 24 and let's say we learn this route from both router b and from router c so this topology table is filled out with two entries for the same route again this is not the routing table yet this is a topology table and it has a metric so let's keep it simple so the metric to router b is 10 and the metric to router c is 20. so for this simple example let's just say that the router now realizes that the successor route the best route is going to be the path through router b now once the dual algorithm has run and it realizes this it then takes that route or that path and it places the successor route into the routing table in this case the ip routing table so now we know the successor is to router b and the feasible successor path is to router c so as we can see it's going to choose the path out to router b now what happens if this route information is lost and router a no longer learns about this this route from router b or from router c and it gets flushed well router a what he's going to do is he's going to send a query to router b and to router c asking do you know about this route because i've lost it and i'm hoping you have information on it and the neighbors will respond back but specifically let's say in this case that router c is the only one that knows about it router she will respond yes i'm aware of it and it will send the information over and router a will say thank you very much and router a will then insert it into the topology table it will become the successor and once it's to the successor it will be placed into the routing table and then router a will then begin using the path through router c to reach that subnet and last but certainly not least we have protocol dependent modules so eigrp and the dual algorithm function in a way that protocols can run and use eigrp independently of one another so ip builds out its own neighboring topology tables ipx and apple talk they all build out their own neighbor and topology tables and dual can work with any and all of them so you've learned a lot in this video that will help you with eigrp design we've done an overview and we've talked about the individual components of eigrp messages algorithms tables and modules you'll need to know all this information not only to design eigrp but obviously to do very well on the ccda exam if you study what's in this video and know it well i'm confident you'll do really well in the eigrp portion of your ccda good luck in your studies [Music] hi this is david voss ccie11372 and in this video we're covering ospf design we're going to begin with some concepts you need to understand a baseline i guess you could say prior to designing ospf and then we're going to get a bit more granular in this video and dig into ospf concepts such as administrative areas virtual links router types designated routers neighbor exchange states link state advertisements and best path selection if you're going to design ospf properly you need to understand all of these concepts we will not go into configuration examples that you can learn in the ccnp route exam but for the ccda you will need to understand these concepts so let's begin ospf is one of the most complex routing protocols that can be be deployed in modern networks ospf is an open standard protocol that is it should be able to run on cisco and non-cisco equipment ospf is a classless routing protocol and this allows it to support vlsm similar to eigrp which uses dual ospf uses spf algorithm to select loop free paths throughout the topology ospf is designed to be very scalable because it's hierarchical routing protocol using the concept of areas to split the topology into smaller sections so it is a very popular protocol in today's enterprise networks because it can scale so well ospf takes bandwidth into consideration when calculating route metrics in ospf it's considered the cost a higher bandwidth generates a lower cost and lower costs are preferred in ospf ospf supports authentication just as eigrp does in rip version 2. ospf is also very extensible it's similar to bgp and isis meaning that the protocol can be modified in the future to handle other forms of traffic ospf discovers neighbors and exchanges topology information with its neighbors acting much as eigrp does in that way based on the collected information and the link costs ospf calculates the shortest paths to each destination using as we mentioned before the spf algorithm the formula for calculating the interface cost is reference bandwidth divided by link bandwidth the default reference bandwidth is a hundred megabits per second but this can be modified just as the link bandwidth can be modified using the bandwidth command please note that the reference bandwidth should be modified in networks that contain a combination of 100 megabits per second and one gigabit per second links because by default all of these interfaces will be assigned the same ospf cost that's obviously a big design consideration and something you certainly could be tested on another aspect that adds to the design complexity of ospf is that it can be configured to behave differently depending on the topology in which you are implementing it ospf recognizes different network types and this will control following actions such as how updates are sent how many adjacencies are made with the ofcpf speakers and how the next hop is calculated ospf supports the following network types broadcast non-broadcast point-to-point point to multipoint point to multi-point non-broadcast and loopback ospf automatically selects the network type that is the most appropriate for the given technology so for example if you configure ospf in a broadcast based ethernet environment it will default to the broadcast type if you configure it on a frame relay interface it will default to the non-broadcast type an ospf configured on a point-to-point serial link will default to the point-to-point network type the only network types that you need to manually assign would be point to multi-point or point to multi-point non-broadcast these obviously are most appropriate for the partial mesh which is hub and spoke environments and these must be configured manually so now that you have a high level understanding of ospf let's go ahead and dig into ospf concepts all of which you will need to know for your ccda exam we're going to go through these one by one to the level of detail you need to know for the ccda exam and we're going to begin with administrative areas an autonomous system is broken out into areas so areas are a group of routers that share a same area id and these different areas these different groupings have different functions and and they know different types of information so you have backbone area standard area et cetera et cetera and each of these areas perform different functions so let's talk in detail about what some of these areas know and maybe what some of these areas do not know but also how ospf is designed around these these concepts of areas so remember we're talking at a higher level here but as is a good rule of thumb um your backbone area in ospf if anybody ever refers to area zero you know they're talking about the backbone area in ospf and this is probably the most well-known area because it is required and all other areas must connect to the backbone area so if for area to area communication let's say you have an area one communicating to an area three both of those areas must connect to the backbone so let's start here with a standard area now a standard area you know you know what does that really mean well standard areas can be thought of as equal opportunity employers i guess you could say because they know about every route in the autonomous system in the ospf network and they share their routes but they also learn all their routes from other areas through the backbone and this is just fine all this route sharing is just fine if routers are high-powered enough to store every route but also to run these complex spf calculations but just know the standard areas contain lsas of type one two three four and five now next you know if you think of a stub area which we'll talk about next if you think of a network you know you have leaf nodes on networks well that's what kind of a stub area is it's handy if devices are lower powered routers are lower powered or simply do not need to know about every route a stub area is similar to a standard area but routers in it are not aware of externally sourced routes directly and in terms of lsas that means that type 5 lsas are not permitted in a stub area stub areas use a default route to exit for traffic to exit a stub area it uses a default route now next would be a totally stubby area and let's take this stub area concept one step further in a total stubby area in addition to the lack of type 4 and 5 lsas type 3 lsas which carry information about internal routes are also prohibited the concept of an injected default route still applies here just like a stub area so all traffic leaving the area does so using the default route and then finally let's go over this concept of not so stubby areas so you know this is an interesting uh i guess you could say concoction because not so stubby areas can connect to non-ospf networks that are not part of this autonomous system and they and they can receive routes from those non-ospf networks or networks that are not participating in the autonomous system and it will receive those routes through redistribution and then it can turn those type 7 lsas and kind of you know basically it's going to mask them and make them appear as type 5 lsas and then begin sharing them onto the network so there's there's your ideas of networks in in areas but all areas in an ospf autonomous system must be as you know physically connected to the backbone area well what if you can't do that you know what if you uh what if you can't connect an area to area zero so let's draw out this concept of a virtual link let's imagine we have our a company on the east coast and we have in this company we've deployed ospf already so we have our backbone area zero and then we have other areas that have to obviously connect into this backbone area so let's say we have an area one in the boston area and then an area to let's say in florida but let's focus in on area one so in the boston area we have area one in boston and we acquire another company in that area and it's easy enough for us to connect this new company into our boston resources so we're going to connect them into our boston router very simply the problem is is that even though this company that we've acquired maybe they're already running ospf and we convert them to ospf area 3 to work within our autonomous system we still need to meet the requirement of ospf where an area must connect into area 0. so ospf allows for what is called as you know the virtual link we will create this virtual link between area three and area zero it's passing through area one and this allows us to meet that design requirement of ospf so route to area 3 and area 0 see this as a direct connection and things will work just fine thanks to the virtual link so there are many different ospf router types that you need to be aware of there's the area border router which connects one or more ospf areas to the backbone area there's the asbr or autonomous system boundary router which will be located between an ospf autonomous system and a non-ospf network and then you have your backbone router which is pretty straightforward a router with at least one interface connected to area zero and then another easy concept and internal router a router with all interfaces in one area let's draw this out real quick let's just to drive it home so let's draw our area zero in an area zero you know already is the backbone so a router within area zero is a backbone router and then we connect to another area let's say area one this isn't this is an area border router pretty straightforward concept there's your abr and let's say we have another area we're connecting to there's another abr but we are also connecting an asbr here because we have a non-ospf network that we're going to be injecting routes from into our ospf process so we are injecting routes in through an asbr converting type 7 lsas to type 5 and those are being forwarded on to the network and then you have last but not least internal routers which have all interfaces in the same area pretty straightforward so in order for two ospf routers to communicate they need to go through this process of exchange state so you need to understand a basic concept of what these are here's the following states there's the init state where a hello packet has been sent by a router it's waiting for a reply from the establishment state where there's the discovery of that hello and then the election of a dr and multi-access networks the x-start stage where a master slave relationship is started between two routers the router with the high router id becomes the master and starts the exchange and as such is the only router that can increment the sequence number then there's the exchange state where the slave acknowledgement acknowledges the master's packets and this information in this state is only lsa headers and that does it and it describes the contents of the entire link state database then there's loading where there's a request for more information in this state the actual exchange of link state information occurs and then there's full synchronization and in this state routers are fully adjacent with one another all the router and network lsas are exchanged and the router's databases are fully synchronized now a designated router in ospf is a key concept that you need to know because on multi-access networks a designated router will establish adjacencies with all other routers on the multi-access network learn all their routes and then share all the routes with all the other routers and then the the bdr the backup designated router will fill in should the dr fail and you can set the dr and the bdr manually and actually you most you should do it this way you should set it using the priority command in ospf so understanding ospf priority is key because you can manually set who the dr is and who the bdr is now it's easy to talk about this and look at a look at a powerpoint and you may not fully appreciate how important this concept really is so let's actually draw it out so on a typical multi-access network let's say we have five routers and you want to establish adjacencies in ospf to share routes between them if they did it that way where they're all neighboring with one another and communicating with one another you're going to see that all these adjacencies are going to add up pretty quickly and that's going to that's going to tax the resources on the routers themselves but it's really unnecessary we can share this information in a much more efficient manner so what we're going to do is we elect a dr in ospf again it has this built in within the ospf design itself or a multi-access network so you can elect a dr and then the dr establishes a an adjacency with all the other routers on the multi-access network it learns all of their routes and then shares all their routes so now we just have four adjacencies required now if the dr fails and those adjacencies fail the bdr would take over now regarding link state advertisements what you really need to know at least just for now in ospf is that a link state advertisement is a packet that contains all relevant information regarding a router's links and the state of those links now there are many different types and i've listed the key types for you here and we're going to dig into detail on these different types as we get into the labs but just for now know that these are these are informational packets that have information on a router's links and the state of those links so now that ospf has gathered all this information it needs to know what to do with it needs to choose best path so it puts all the information in a topology table and then ospf the metric for ospf is cost so cost is 10 to the power of eight divided by bandwidth and lower costs are preferred so the best way to understand cost is actually for us just to draw this out to see how it works so let's draw out a six router network and let's say we have router one which ultimately wants to communicate with a network off of router 6 and it will have two choices two paths it can possibly take it can go via router 2 or via router 4 to this network we'll say 192.168.10 network 24. which is hanging off router 6. now router 1 then calculates using ospf the cost for each and every link in this path and it's going to do the same for the path from router 2 and 3 to 6. and then what ospf is going to do is add up the entire cost to get to router 6. so from going via router 4 that path has a total cost of 20. and going via router 2 that path is a total cost of 25 and we know that ospf uses the lower cost to make its decision on which path to take so the total cost of 20 wins out and we will choose router 4. now that being said let's say a new network is introduced that has higher bandwidth links and even though we have more routers or more hops through this network let's say there are four hops if the cost is low and for this case we'll say five five one one and one if the total cost here is just 13 even though there's more hops ospf is going to choose this path because it's more efficient so that's cost basically explained it's cost in a nutshell so here's what you've learned you've received an overview of ospf and then we got a bit more granular to the level you'll need to know for the ccda exam including administrative areas virtual links router types designated routers neighbor exchange states link state advertisements and best path selection i'm confident after watching this video if you know this information well you're going to do excellent on the ospf portion of your ccda exam good luck in your studies hi this is david voss ccie11372 and in this video you're going to learn about isis design specifically you're going to learn about isis operations areas addressing packet types network types and metrics so let's begin in recent years the isis routing protocol has become increasingly popular with widespread usage among service providers it is also a very flexible protocol that's been extended to incorporate leading edge features such as mpls traffic engineering the isis routing protocol is a link state protocol as opposed to distance vector protocols such as igrp and rip isis protocol is an intra domain osi dynamic routing protocol isis uses a two level hierarchy and it's used to support these large routing domains a large domain may be administratively divided into areas from a high level isis operates as follows routers running isas will send hello packets out all isis-enabled interfaces to discovered neighbors and establish adjacencies routers sharing a common data link will become neighbors if their hello packets contain information that meets the criteria for forming an adjacency routers may build a link state packet lsp based on their local interfaces that are configured for isis and prefixes learned from other adjacent routers and a shortest path tree is calculated by each is and from this spt the routing table and from this the routing table is built next let's talk about areas and the routing domain within isis so an isis routing domain is similar to bgp autonomous system a routing domain is a collection of areas under an administration that implements routing policies within the domain first let's talk about the backbone iss does not have a backbone area like ospf area 0. the iss backbone is a contiguous collection of level 2 capable routers each of which can be in a different area speaking of areas within isis an individual router is only in only one area and the border between areas on the link that connects the two routers that are in different areas and the border between areas is on the link that connects two routers that are in different areas this obviously is in contrast to ospf so as you've already heard isis has a two level hierarchy contiguous level 2 capable routers from the backbone both level 2 and level 1 routers live in areas routers can be level 1 level 2 or both level 1 level 2. within the cisco ios software the default configuration is both level one and level two at the same time this allows isis network to run with minimal configuration in more of a plug-and-play fashion level two capable routers connect all areas within a routing domain level 2 routers advertise their own nsap address to other two other level 2 routers in the backbone in all level 1 routers and hosts in an area must have an nsap with the same area address a level 2 router may have neighbors in the same or in different areas but it has a level 2 link state database with all information for inter area routing level 2 routers know about other areas but will not have level 1 information from its own area a level 1 and level 2 router may have neighbors in any area it has two link state databases a level one link state database for intra area routing and a level two link state database for inter area routing next let's talk about nsap addresses an nsap describes an attachment to a particular service at the network layer of a node similar to the combination of ip destination and ip protocol number in an ip packet an nsap address has two major parts the idp or initial domain part and the dsp the domain specific part the idp consists of a one byte authority and format identifier that's the afi in a variable variable length initial domain identifier the idi and the dsp is a string of digits identifying a particular transport implementation of a specified afi authority everything to the left of the system idb can be thought of as the area address of a network node the big difference between nstap style addressing and ip style addressing is that in general there will be a single nsap address for the entire router all is's and ess in a routing domain must have system ids of the same length all routers in an area must have the same area address all level 2 routers must have a unique system id domain wide and all level 1 routers must have a unique system id area-wide all ess in an area will form an adjacency with a level one router on a shared media segment if they share the same area address if multiple nets are configured on the same router they must all have the same system id next let's talk about packet types there are four types of packets each type can be level one or level two first there is the intermediate system to intermediate system hello packet used by routers to detect neighbors and form adjacencies then there's the link state packet there are four types of lsps level one pseudonode level one non-pseudo node level 2 pseudonode and level 2 non-pseudo node complete sequence number pdu csnps contain a list of all lsps in the current database cnsps are used to inform other routers of lsps that may be outdated or missing from their own database this ensures all routers have the same information and are synchronized and then finally partial sequence number pdu psnps are used to request an lsp an acknowledged receipt of an lsp next let's talk about network types the types of networks that isis defines include point-to-point and broadcast networks point-to-point networks such as serial lines connect a single pair of routers a router running isas will form an adjacency with the neighbor on the other side of a point-to-point interface automatically the dis is not elected on this type of link the basic mechanism defined in the standard is that each side of a point-to-point link declares the other side to be reachable if a hello packet is received from it next there's broadcast networks such as ethernet even token ring these are multi-access and they are able to connect more than two devices all connected routers will receive a packet sent by one router on broadcast networks one is will elect itself the dis the dis is responsible for flooding and it will create and flood a new pseudonode lsp for each routing level that is participating that it is participating in that is level one or level two and for each land to which it is configured and connected a router can be the dis for all connected lands or a subset of connected lands depending on the configured priority or if no priority is configured the layer to address and then finally nbma networks such as frame relay or atm or x25 can connect multiple devices but have no broadcast capability all other routers attached to the network will not receive a packet sent by this router special considerations need to be taken in account when configuring isis over these types of networks because isis considers these media to be just like any other broadcast media such as ethernet or token ring in general it is better configure point-to-point networks on wan interfaces and sub interfaces next let's talk about isis metrics cost is the default metric and is supported by all routers while some routing protocols calculate the link metric automatically based on bandwidth such as ospf or bandwidth and delay such as eigrp there is no automatic calculation for isis using old styled metrics an interface cost is between 1 and 63. all links use the metric of 10 by default the total cost to a destination is the sum of all costs on an outgoing interface along a particular path from the source to the destination and least cost paths are preferred the total path metric was limited to 10.23 this small metric value proved insufficient for large networks and provided too little granularity for new features the cisco ios software addresses this issue with the support of a 24-bit metric field the so-called wide metric now metrics can have a maximum value of as you can see right here deploying isis on the ip network with wide metrics is recommended to enable finer granularity and to support future applications such as traffic engineering so you have learned quite a bit about isis you've learned about isis areas and router types the nsap address as well as pekka types network types and metrics all this information will be needed on your ccda exam and i'm confident if you've studied this video well you're going to do very well on your exam good luck in your studies [Music] hi this is david voss ccie 11372 and in this video we are going to cover bgp design the first thing we're going to do is do an overview of bgp and then we're going to get a little bit more granular and we'll talk about bgp path attributes bgpas path ebgp versus ibgp public versus private asn bgp updates and how bgp advertises routes all this information you will need to know to understand how to properly design bgp and do well on this portion of the ccda exam so let's go ahead and begin with an overview of bgp bgp is an exterior gateway protocol that uses autonomous system numbers uses tcp 179 to communicate between neighbors and it really is a protocol that requires manual configuration for almost everything it doesn't really do anything unless you tell it to do it which i really like about the protocol now it uses path attributes which are key in decision making on choosing best route so path attributes define information about a path but also this information can be used to help decide upon the best path and we will draw that out in a minute here so you can understand that better now regarding bgp path attributes there are some that you absolutely have to know and memorize the first is weight weight influences a best route for the local router and obviously it's manually configured local preference influences the best route for all routers in an autonomous system so this is a shared attribute a s path lists the number of autonomous system numbers in the path and this can be manipulated origin is a value implying if the route is from an igp or an egp and finally the med which can influence the best route for routers in another as so you can influence traffic flows into uras by sending out the med to other other routers so here you can see we have two routers that are in autonomous system 700 and then upstream we have another router and autonomous system 140 and autonomous system 87. so here you see there are four hops but as far as bgp is concerned it's just counting ases so it counts one two three asses the as path is 700 140 and 87. why is this important to know because here's another flow that has two routers in as700 and then one router in as87 now according to this path there's just two as's that would be the preferred path it's critical to understand that bgp is concerned about a.s path and not so much about hop count aspath is a key attribute to understand now internal versus external bgp ibgp is something you would run basically interior to your company it's bgp connectivity within the same autonomous system in this routers do not update as aspf normally they should never have to because you're running the same autonomous system and in ibgp things should always be meshed routers should always be fully meshed and there are ways you can get around this and we'll talk about that in a little bit now ebgp is external connectivity to other as's and routers do update the as path in those cases so let's say we have an autonomous system 200 and in our company we're running ibgp full mesh between all routers and let's say we have connectivity to two upstream providers one is autonomous system 301 and the other provider is autonomous system 450. now between ourselves and our providers we are running ebgp because it's two different as's and internally we are running ibgp because we are communicating between the same a s now configuration between ib gp and eg ebgp is quite similar the main difference is you're choosing to communicate with the same as or a different as now let's say we want to communicate to a web server over the internet and we have a certain amount of hops now let's say one of those paths through as450 takes us through quite a few more hops but it takes us through fewer as's so let's just say for example we go through as900 and then as100 so that's 450 900 and 100 those are the three asses we traverse in order to reach that route now let's say on this flow through autonomous system 301 we go through fewer hops but more as's now even though there's fewer hops because there are more as's we're not going to prefer this route there are five as in this path that is not going to be preferred to the other path which has only three ases so we're going to choose that path we'll choose the 3as path now let's say we're running a web server inside of our company and we're running ibgpu between these three routers and we're connecting to two upstream providers using ebgp and let's say we have users on the internet who are trying to get to this web server we can manipulate the as path attribute in bgp to make them prefer one path over the other and the way we do that well let's say our autonomous system is 50 we can manipulate the aspath attribute by adding to the as path on one of our links so for example the users know that they can reach the web server via 1as well we're going to increase that on the top router and we're going to manipulate it manually and add our as over and over again to the aspath attribute and the users as far as bgp is concerned that now is a longer path and therefore the user will prefer the bottom path because it's only one hop one 1as hop now if that router were to fail users would then prefer the other path so you see you can manipulate traffic flows that way now you need to understand the concept of public and private asn's and this shouldn't be foreign to you because you understand public and private i p addressing so autonomous system numbers are chosen from this pool and you can use them for private use or public use as need be but you should be aware of that chart now regarding bgp updates that we receive from neighbors you can receive from your provider a default route only which many people do or you can receive a full bgp routing table that is literally every route that's available on the internet or you can receive just partial updates and that is maybe the provider knows about certain routes via a better path than most other providers you can just receive a partial update from your provider so you should know that you can receive those three different types of updates that should be known for your ccnp route exam now regarding advertising routes advertising bgp routes can be done four ways either through the manual network command redistribution of bgp and igp or propagation of existing bgp routes or again manually using the aggregate address command maybe the best way to explain these is to simply draw it out now imagine we have a router with an i bgp connection and an ebgp connection to an upstream provider so there's our ebgp connection here's our ibgp connection and we're autonomous system let's say 400. so on a router we can advertise in four different ways we can manually specify the network we want to advertise by literally typing it in network 10.10.10.0. or network 198110 and we can forward that via ibgp and or ebgp the other way is we can learn routes via bgp and redistribute that route into let's say an interior routing protocol let's say if we're running ospf we can take the the routes we learned from our ebgp neighbor and redistribute them the other way is to simply pass the routes we're learning from our ebgp neighbor via bgp internally to our ibgp neighbor so that's just pat forwarding the the information on and finally we can again manually set an aggregate address on the router and that's a manual configuration to aggregate some of the routes and again that can be advertised out either way so the rule of synchronization in bgp you should simply know this that bgp will not advertise a route unless it knows about that route via an igp that's what you really need to know for the exam now you can disable this by typing no synchronization on your router and then it will simply forward routes that are not in the igp so here's what you've learned you've received an overview of bgp and we dug in a little bit on bgp path attributes aspath ebgp and ibgp public and private asn bgp updates and then the advertisement of routes all this you will need to know for your ccda exam and if you master this material i'm confident you will do very well on this portion of your ccda exam good luck in your studies [Music] hi this is david boss ccie11372 and in this video we'll be covering ip version 6 routing protocols so here's what you're going to learn you're going to learn about ip version 6 routing protocols an overview of them and how to enable them to support ipv6 all of the ipv4 routing protocols had to go through adaptations each had to be changed to support longer addresses and prefixes and the actual message is used to send and receive routing information have changed in some cases as well using ipv6 headers instead of v4 headers but in particular like their ipv4 versions each version 6 igp uses v6 multicast addresses those are just a few of the changes but even with those changes each ipv6 igp has many more similarities than differences compared to their respective version version 4 cousins let's start with rip the overall operation of rip next generation closely matches that of rip version 2. routers still send periodic full updates with all routes no neighbor relationships occur the continuing periodic updates also serve the purpose of confirming that the neighboring router still works the big difference between rip version 2 and rip next generation configuration is that rip next generation discards the age old rip network command and replaces it with an enable interface sub command finally rip next generation allows multiple rip next generation processes on a single router so an ios requires that each rip next generation process is given a text name that identifies each rip next generation process for that one router and there's another difference compared to rip version two let's go ahead and jump into our lab in our lab we're going to be working on router 2 and router 4 and we're going to go ahead and log in and enable rip let's take a look at our interfaces on router 2 and we're going to be working with serial 0 and loopback 1. now the first thing we'll do on router 2 is we're going to go ahead and assign ipv6 ip addresses so on interface zero zero zero even though it has an ipv4 address we obviously can still add an ipv6 address and again we're gonna shorten that so it's a lot easier we're gonna use the uh the ability to shorten that address using the double colon and then the loopback address will place in a different subnet so we're going to use 2012 and 2017. well let's go ahead and enable rip next generation on router 2. and before we can do that we need to enable version 6 routing see by default a router will route version 4 but not version 6. so we do that by typing in ipv6 unicast routing and then we can enable our routing protocols so next we go to each interface we want to enable rip on so first we'll go to interface serial zero zero we simply type ipv6 rip and then we need to give it a process name the the rip process and we can run multiple multiple processes on this router we don't use number we will use actually a name and we can name it pretty much anything you want for simplicity's sake we'll just say our process name is routing rip ipv6 rip routing rip enable so we've enabled it on interface serial zero zero we will go ahead and do it on loop back one as well inserting it into the same rip process now rip is still not running on this router until we enable it globally and we do that via ipv6 router rip and then the process name which we have chosen as routing rip now we will verify that it is running on router 2. so ipv6 protocols there it is and you see the interfaces as well that are inserted into the rip process now that being said we're not learning any routes because we are not we've not established any neighbor because we haven't learned any routes from any other ipv6 rip routers so on router 4 we're going to go ahead and assign ip addresses to the appropriate interfaces this on serial 0 1 is the point to point so we will end this ip address with a dot 2 sharing the same subnet and then we will insert loopback 1 into rip ultimately and we're gonna go ahead and assign it to zero one eight so it's different than router two router two's ip address was two zero one seven and then we're gonna go ahead and enable rip on this router and again we need to enable unicast routing for version 6. we need to insert the interfaces into the rip process and again we'll use routing rip as our process id and here we've enabled it and let's do the same on loopback one and it's as simple as typing up arrow now and then finally we will enable it globally and now you will see when we do show ipv6 protocols that it's enabled on router 4. and now we can take a look at ipv6 rip and this shows what interfaces are participating the administrative distance and update intervals and here's our routing table so we are learning the route from router 2 which begins in 2017 so that is actively being advertised via rep and so we have version six that is rip next generation up and running between router 2 and router 4. it's rather straightforward and on router 2 you will see the loopback from router 6 in his routing table as well so pretty straightforward next let's talk about eigrp cisco originally created eigrp to advertise routes for ipv4 ipx and apple talk this original eigrp architecture easily allowed for yet another layer 3 protocol ipv6 to be added as a result cisco did not have to change eigrp significantly to support version 6 so there are many similarities that exist between version 4 and version 6 versions of eigrp that being said there are some differences and i've listed what you really need to know for the ccnp route exam so let's go ahead and enable eigrp between router 2 and router 4. so we already have ipv6 up and running let's go ahead under interface serial 0 0 enable eigrp ipv6 eigrp we're going to use the process id of 10 and under loopback 1 we will also use the process id of 10 and then very simply we just need to enable eigrp globally and we do that via ip version 6 router eigrp process id 10. and again we have to do a no shut and if we look now we under ipv6 protocols we can see eigrp is running and the interfaces that are participating pretty straightforward but again there's no communication with any eigrp neighbors so let's go ahead and you'll see here the topology table for router 2 which just shows the local routes but again this idea of successor and feasible successor should look familiar to you as it is in ipv4 so now on router 4 we are also going to go ahead and enable ip or eigrp and again we're going to use eigrp process id 10 enable it under each interface that we would like to participate and then enable it globally once we do that the neighbor relationship between router 2 and router 4 will come up over this point to point link and we will see our neighbor right here so again you can see we have hold time up time looks looks very familiar to ip version 4. it should look very familiar so in many ways we're kind of slaying the beast once you get your hands on ipv6 it actually begins to look pretty familiar let's look at our topology table and we will see what we've learned not only locally but from our neighbor and then finally let's take a look at our eigrp routes and there is the loopback from router 2 which we are learning on router 4 via eigrp again pretty straightforward now regarding ospf in order to support ipv6 an ietf working group took the ospf version 2 standard and made changes to the protocol to support version 6 resulting in the new protocol named ospf version 3. to migrate to ipv6 routers run ospf version 2 for v4 support and version 3 for ipv6 support finally let's go ahead and enable ospf between router 2 and router 4. so on router 2 again we're using serial 0 0 and loopback 1. we're going to place loopback 1 in a different area than serial zero zero though so in interface serial zero zero we're gonna make that area zero so ipv6 process id 10 we're going to insert it into area zero and loopback one we're going to insert into area 24. so this is not done like ipv version 4 obviously there's a pretty big difference here you're enabling it under the interface itself now we do need to enable ospf globally still though it may not be identical to version 4 but it does need to be enabled globally so we do that by ipv6 router ospf the process id and that is it now let's go ahead and enable it on router 4 as well and we're going to do the same it will be for serial 0 1 and loop back so again under both interfaces we enable ospf via the ipv6 ospf process id we're going to insert the point-to-point interface in area 0 and the loopback interface will assign to a different area which is will create area 34. and then we enable ospf globally again process id 10. and let's go ahead and take a look at our ospf routes and there we have learn via ospf the loopback from router 2. we can look at our ospf neighbors there is rudder two as our neighbor again this should look pretty familiar to version four uh version six ospf support it does not look all that different than version four and here you see the lsas you can see the similarities between ospf version 2 and version 3 there's quite a few of them and understanding the concepts of version 4 will certainly help you in understanding how version 6 works so here's what you've learned you've had an overview of each of the version 6 routing protocols that you'll need to know for the exam and then you've seen actually how to enable them in the lab i wish you the best of luck in your studies thank you

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Length: 92min 27sec (5547 seconds)

Published: Thu Nov 04 2021